Something like 95% of professional DotA 2 games end with a concession, whereas I have personally never seen a professional LoL team concede even once, no matter how hopeless the game (though I hear it happens in LCK). Is this a difference of mentality? Does Riot not allow concessions? What gives?
There have been concessions in professional LoL. The most notable example I can think of is at IEM Katowice in 2016, Fnatic conceded at 22 minutes to SKT T1 during game 3 of a best-of-5. It generally happens at tournaments where there's a massive skill difference and the losing team concedes out of fatigue. In the case of MSI, Fnatic was on their 4th Bo5 in two days and knew they were hugely outmatched so they conceded instead of drawing out an exhausting, losing game.
Mentality plays in part. It's seen as poor sportsmanship by some, most fans want to see it play out and hope for a huge upset rather than a team conceding out of poor morale. Comebacks and backdoors are frequent enough in League that teams and fans will still feel like there's at least some chance and try to play it out. C9 vs Samsung Blue at 2014 Worlds is a good example of this. C9 was clearly outmatched but they played out the entire series in hopes of getting an upset.
I've only played a few games of Dota in my life so I might be wrong here, but it seems that games end much faster in League than Dota. Cracking a base and killing the Nexus is much easier in League. In the few games of Dota I played, it took a long time(5-10 minutes) to crack the base and get onto the Ancient/Nexus/Immortal. In League, teams can break into a base in just seconds after a wipe if enough survive the teamfight. So it makes sense that if you're being sieged in your own base in Dota, you'd concede instead of drawing out a long closure, while in League it's so fast you might as well play it out since you won't save much time. This is all pure conjecture though, I'm not that knowledgeable about pro Dota.
Another point thanks to @Cronax: comebacks are FAR more likely. In the late-game, even if the enemy is beating on your Nexus, if your team can somehow manage to win the teamfight and kill them all, this can give your team enough time to kill the enemy nexus instead.
I want to add a somehow different view on this, as most answers so far seem to come more from the League of Legends player/viewers POV.
I think the main reason for the really high number of games finished by concession is due to the way concession in DOTA2 works: In DOTA2 there is no formal way of concession except in tournament games where Writing "gg" or using the Chat Wheel's "Good Game" Emote and then veryfing their concession in an onscreen popup.
As it is mannerly for pro players to wish "gg" at the end of a game, they usually concede it at a point where the whole team or atleast the core heroes are dead and the enemy team is already hitting the Ancient (Main Building).
This might happen even earlier when the whole team got wiped as Barracks, unlike Inhibitors in LoL, don't respawn. Additionally, Heroes in DOTA2 might end up with a really long death timer (2 Minutes might happen in a normal game when a hero dies after buying back). So there might be a case where "gg" is called before they even attack the Tier4 Towers (the ones directly infront of the ancient) because it is clear that they won't be able to defend for over a minute with only two supports, to allow their teammates to respawn.
Just to add to this, I don't think most DOTA2-players see calling gg in the above instances as concession, as it is mostly at the point of no return.
I can provide a different view to most other answers here, because I've had the opposite experience -- lots of time on Dota 2 while only 10 or so LoL games.
In most pro Dota 2 games, teams concede after they throw everything they have at the enemy to stop them pushing the base. I'm not sure about LoL but in Dota you can buyback your hero to respawn immediately, at the cost of a lot of gold and extra respawn time when you next die. So a lot of times, the defending team will lose most of their heroes, then proceeed to buyback the dead ones and make a final stand. Any heroes that die then would be out of the game for potentially a long time (up to 2 minutes), so it's common for teams to concede in situations like that.
To answer your question, I think the answer is the same for both games: there is always the chance for a comeback. Dota 2's comeback mechanics are pretty insane in the current meta, meaning if you get a kill on an important carry you may very well be back in the game. Again I'm not sure about LoL, but I know that Inhibitors respawn (unlike the Dota equivalent of barracks), and natural
Very rarely do teams call GG before they try everything, but it does happen. I can't think of any specific games - if anyone knows then feel free to add a comment or make an edit.
Of course there's also this classic 0 minute GG. (They withdrew it quickly!)
This is a good question, when I was playing lots of DOTA 2 there was no concede option, so I'm going to assume they added one obviously.
The reason this would be the case in DOTA 2 is that the game is much less forgiving than LoL, especially when a carry starts to "snowball" - the carries in DOTA 2 are a lot scarier than LoL and when they get strong they are insane. With pro players, their carries can farm so well combine this with some early and mid game kills they will quite literally be unstoppable along with their team. DOTA 2 has a lot of items you can buy that have strong actives. When their carry has a level advantage and a ton of strong items, they can shred the enemy team really quick, so I'm thinking the pros can identify this and know when the stop trying.
The items I was mentioning (and I know many have been added since I played last, I was playing when earth spirit was introduced and before that since beta) are stuff like:
Black king bar, which makes it so you are not effected by almost all spells, stuns, etc for some pretty long time once you have used It a couple times.
Skull Basher, gives your auto attacks a chance to cause mini-stuns
There's a weapon that gives you a spell that is like Sion's stun in LoL
There's an item called Manta Style, which when activated, creates 3 copies of your hero that can attack with you and make you harder to target.
Theres an item that can let you get the blink ability, so you can instantly teleport to areas within a certain distance every "X" amount of seconds.
So combine the snowballing and the levels plus gold it gives, with really strong carries and items, I could see how there are concessions a lot.
In League, comebacks are quite possible if the losing team outplays the winning one. A large part of pro games is not just winning but also the viewing experience.
I've heard from people that competitive Starcraft had problems where it was just getting boring to watch people micro the same thing each game for 10 minutes, then conceding on one mistake. (Just to note, I haven't watched many Starcraft games myself, this is based on what other people have said)
Having a losing team come back spectacularly is incredibly entertaining to watch and creates very memorable moments for the eSport.
You're also (obviously) statistically more likely to win if you never surrender vs surrendering when you start losing. You either lose either way or pull it back and win. It's not like they really have a time limit on the game's lengths when they're in the Arena, vs maximising wins for time on the solo ladder either.
In my opinion it is because LoL has more catchup mechanics.
- Inhibitors (barracks) respawn
- As turrets in a lane are destroyed, the opposing minions get stronger (easier for losing team to farm)
- Gold cap is lower; it's easier for a losing team to hit full build and therefore be on even material footing with the opponents
- Level cap is lower; it's easier for a losing team to hit full level (18)
It's less likely you'll catch up and win from a losing position.
Also, DotA games are longer on average, so there's more time at stake in playing out a losing game.