For a long time I asked myself the same question. Never found a very satisfying answer. In the meantime I stopped playing Dota 2 (which often has griefers) and Battlefield (which often has cheaters) so I’m not so troubled by this issue anymore.
I think devs just don’t care and leave dealing with these kinda folks up to the players just because it’s the status quo and nobody pushes them to do anything about it.