Anyone with proof that reporting a player for leaving actually gets them banned?
So far I've seen games where players have +100 leaves. So that's enough proof that reporting leavers doesn't work. FAIL
It seems you have not thought your statement through. Next time don't speak in such absolutes and learn how the system that you are putting down actually works. Fail.
Besides, I am fairly sure Riot only bans people for verbal harassment which is why that is the only thing you can report from the end game screen.