I believe the loot system changes in WoW were inspired by occurrences of groups of people joining matchmaking together, then kicking a person after the boss died and taking all the stuff for themselves. I only saw this sort of behavior firsthand once or twice, but I’ve heard from others who thought it was widespread.
And in WoW too, given how the honor rank system works, imagine if people could kick others from battlegrounds: they would kick those with higher ranks so they could climb the ranks faster themselves.