In general the idea of "just use filters" fails. Number one, messages cost money for someone somewhere. Allowing everything and just filtering out bullshit leads to untold amounts of bullshit you have to filter. Hence the point of moderators in the first place...
This feeds into point two. Most people don't want to play moderator and create huge lists of filters in order to not deal with shit. They will gladly farm that off to someone else even if there are considerable potential negative side effects, and if it gets too bad they will pack up and move to a new community with less negative effects.
> Most people don't want to play moderator and create huge lists of filters in order to not deal with shit.
Sure — but think of Ad block filters. Filter lists eventually get developed (eg Easylist), and if the maintainers ever do something radical, users can easily remove one filter list and substitute another.
It’s much harder for users in communities with moderators to do the same — if I get banned from /r/detroit and I live there, what’s my alternative?
This feeds into point two. Most people don't want to play moderator and create huge lists of filters in order to not deal with shit. They will gladly farm that off to someone else even if there are considerable potential negative side effects, and if it gets too bad they will pack up and move to a new community with less negative effects.