A simple and very very old example is email. Even back in the 1990s days of the Internet, we had spam on email and if your reputable isp caught you spamming you’d be in trouble. Same with shitposting on usenet.
Sure there are nuances to consider as to what providers should do and what they should not, but like a lot of things this is a hard problem. The ‘simple’ solutions presented here and in other places will not solve it.