If you asked people who run their own social networks on KnownHost hosting, the most common answers would revolve around privacy, control, free expression and data retention.
Most public (free) social networks have complex controls on privacy, making every posts, response, conversation or file potentially visible to someone who shouldn't be able to see it, as well as the fact that some other for-profit company has complete access to your private matters.
Being able to approve or ban users gives you administrative ability to control your network, limiting it to just the people, employees, or group(s) that you choose.
Regardless of which political party you support, or none at all, you've surely heard about how the free speech of one or another has landed people in 'Facebook Jail' or has resulted in people being banned from the network for saying/sharing something controversial. With your own social network hosting, you remain in control of these matters.
Public social networks come and go like fashion styles. There's nothing worse than losing your entire history of events because someone else couldn't manage their P&L. Hosting your own puts you in charge. KnownHost automated backups make sure you've got redundant copies to preserve your history - making you the owner and not some 3rd party.