There's a cost (both time and money) associated with spreading knowledge through USPS or similar physical mediums. The cost of spreading ideas is virtually free on social media so there isn't much of a barrier to prevent the ideas spreading like wildfire. Good or bad.
What about the costs of having the platform centrally regulating the content on the platform based on an arbitrary, context-free, highly politicized, and ever expanding definition of 'socially unacceptable' content?
We all knew that when FB and Twitter started to centrally control content well beyond the obviously really bad stuff (ie, gore, child porn), that mandate would forever expand and expand, where it's almost impossible for FB to not be criticized for not doing enough ...Absent a massive expansion of content controls, which means massively expensive, which mean incentivizing a) simply limiting the ability for people to communicate on the platform AND/OR b) automation. Which ultimately means countless false-positives and examples of bias by machines trained by the most vocal special interest groups deciding what is okay and not okay to say to another person.
The future is going to feature some interesting trolling to see who can game algorithms to get topics banned on social media through phony media outrage campaigns, false reporting, and social engineering.