[shadowgovt]

a) because services like Twitter and Facebook have to show something in the timeline. What they show is this job

b) because in practice, an approach too laissez-faire here has negative impact both on customer adoption (most people don't actually enjoy cesspools, and they leave when they decide a service is one) and regulation (even in countries with broad free-speech protections, some communication is de facto illegal and there are consequences for a service taking no responsibility for keeping their house in order).

[_chu1]

Almost like these services are more trouble than they're worth.