Leavers are the weak link

My experience, in quick play at least, is that the leavers are often the weak link. Once a backfill comes in, many teams I've been on will go onto victory.

So leavers are really those players who can't meaningfully contribute to the team's progress. If you're a leaver, maybe sticking around for the whole game will help you learn to be a player that could actually carry your team.