Maybe if someone rage quits the computer which is added could be a very good one. Not the usual normal, whimpy one, because most people are a lot better than the computer controlled players. So then when someone rage quits the whole team is better instead of being worse.
Also it's unfair if there's a penalty to quiting. Sometimes I'm distracted and have to go and I'd hate it if then when I'm enjoying the game but have to go, I'd get a penalty.