I just spend half an hour typing this and then I got logged out, so here's the gist
if you leave a game, you have to wait until the game you left is over to join another game.
This isn't really meant as a solution to leaving since you can still suicide into vet or try to die, but it gives leavers a penalty. Either they play the game, or they try to die which in a lot of cases is reportable for gamethrowing. It forces people to play and prevents them from just leaving games until they get the role they want.