I think it's because it's raw and honest and not hidden behind a bunch of allegory that makes it sometimes feel better than other types of writing. That or it's cathartic to be able to declare something done even when it's less than a page long.
I'm not sure I've ever put much thought into it. In theory it seems like a good idea, but it's a slippery slope. One person's joke can be another's cyberbullying. It's complex, and even though it would be nice not to have trolls and bullying on the internet, not only is it probably borderline impossible to completely prevent, I'm not sure I'd want to be that intrusive on someone else's freedom to express themselves. In the end, the internet is just words, after all. A simple misunderstanding could be interpreted as deliberate animosity, and situations like that could make the whole thing rather complicated.
So I suppose you could say I prefer what we have now: just the ability to block those we don't want to deal with.