Pro players always make these little circular steps when fighting creeps. Why is that?
Honestly, this has nothing to do with auto attack on or off. Or standing still for that matter. You can be constantly moving, but not be applying the side step or animation canceling technique.
There are 2 main reasons why would you would do this side stepping as you would call it.
In both Dota and Dota 2, there is a mechanic called animation canceling. When your hero attacks a unit, the damage gets inflicted upon the unit before the animation is finished. So by side stepping really quickly, and then attacking again, you are able to cancel the ending of your first attack animation and then proceed to initiate another attack animation. This is widely used in the jungle as it increases the number of attacks you can deliver in a specific period of time.
Another reason to do this side stepping is positioning. For example, let's say you are on radiant side, and at the bottom of a creep wave. But perhaps you want to be north of the creep wave and take an offensive position, while pushing the wave. The most efficient way to keep the pushing at a maximum is to hit a creep, animation cancel by taking a step forward and repeat.
EDIT: For melee heros, you side step after the damage is inflicted. For ranged heros, you side step after the projectile is released.
Most of pro players have "auto-attack" option turned on,meaning if they don't move they will attack enemy creep...which they don't want to do unless it is the killing blow.
Some people just stand near creep they want to last hit and keep pressing the stop button until creep HP falls in the last hit zone...but by doing this they are revealing their intentions to the enemy.
On the other side all those micro moves and changes of position are really annoying and confusing to the eye making it harder for your enemy to focus lasthitting/denying.
It's mostly just a rhythmic thing. Your hero's attack speed increases as the game goes on and agility/attack speed increases, which changes the attack point of your character. By constantly cancelling the cosmetic backswing of an attack animation, they can know more accurately how long an attack will take. This is crucial during teamfights for heroes who rely on their autoattack and is not something you want to have to think about.
When farming creeps, players also want to minimize the amount of time that they're close to the creep wave, as that's the most exposed a hero should be when farming. By darting in for the last hit and then immediately pulling back, they minimize vulnerability while staying mobile and unpredictable, which is a big help against most skill-based initiation abilities.
I know of three probable reasons for this:
- Avoid standing still. You never know what the enemy might be planning and if you're always on the move they will have a harder time initiating properly on you.
- Moving closer to the next target while maximizing attack time.
- Simply to "keep on your toes" and not lose focus.
There is also a common misconception that moving slightly between each attack would actually let you attack more frequently, by canceling part of the backswing animation. This has to my understanding been proven false in Dota 2.
Pro players' goal is to get as much money as possible while minimizing risks. Usually this is done by farming while not pushing the fight on the lane to the enemy turret. The easiest way to do this is to hit the enemy creep right before they die, so you get the last hit and the money that comes with it.
There are two ways to focus on last hitting:
- Move around a lot, smaller steps allow faster reaction time, because it keeps the cursor close to the hero on the screen.
- Use the stop (default S) action, which keeps the hero stationary and inactive.
Staying completely stationary usually makes it easier for the enemies to come up with their evil plans, so it's a good idea to stay on the move. This is why the first option is generally used.