While watching the League of Legends tournament teams ban between 3-4 champions, you'll see picks like Eve, Xerath or someone very atypical of tournament play.
Someone will do this while the rest of the team goes serious picks. When they remake the game (which I also don't understand the perpose of) they do joke bans and inevitably the person with the Eve (or whichever) will pick someone else.
Why do they do this?
First of all, let's clarify the question. This situation will only happen during online tournaments. During offline LAN events, players have infinite RP and IP as well as every champion purchased. During online tournaments though, players use their standard LOL profiles. As a result, there is a decent chance that some summoners will be missing heroes. When that happens, a placeholder champion that never gets actual play like Eve is chosen instead and replaced with the intended hero later on.
As for why they don't just pick the heroes as soon as they are available? In the current meta, the top and middle lanes are solo lanes. Since solo lanes are 1v1 battles, having to face an enemy who counters you can be too much to overcome. As a result, teams try to pick these two lanes last, in order to avoid getting countered.
The order in which champions are picked is important. As an example, if you start by picking Katarina, the enemy might pick Blitzcrank, Soraka or any number of champions which can immediately shut her ult down. However, if you're last pick and the enemy doesn't have much hard CC, Katarina would be a safe pick!
In draft games players can swap champions after everyone has chosen one, so if your AP mid feels like Katarina might be a good choice but happens to be one of the first picks, s/he can choose a champion for a different role and defer the Katarina pick until it's too late for the enemy to react. But if the last pick on your team doesn't have Katarina s/he can't pick her and you won't be able to swap...
Well, tournament games aren't supposed to be about how many AP champions your support player owns! Your last pick player chooses a different (usually unpopular) champion and announces through chat which champion it really is. After picks are done in this fashion, the game is remade with everyone picking the champions they would have swapped to. In this case no one cares about bans as long as you don't ban anyone that was picked :)
You can also do this the other way around, having someone pick up a contested pick early on even if s/he doesn't own that champion.
They use this placeholder mainly because the player does not have a certain champion. They switch champions to counterpick so not every player gets their own champion. They will switch at the end. As I saw on a stream yesterday Player 4 did not have shyvana, so they used eve as a placeholder. Then the team sayst he name of the champion they want in chat to the other team. After that they will just pick serious picks. Then they restard and they will do everything again but now everyone will pick the champion he wants. This will not occur in soloqueue and ranked :P.
