Bans for feeding

If I'm 0/15/0, I must be feeding and I deserve to be banned right? But wait, what if all my allies were also 0/15/0? Doesn't that mean that we just got stomped thanks to Riots amazing matchmaking system, or that the majority of us just didn't want to play and were held hostage by one or two ass holes that kept voting no? And wait, what if we had 2 people AFK? Am I not supposed to die a lot in a 3v5 game? Why does the banning system not take this into account, and don't say that it does?