There are two places where a blockchain would be very useful in this context: guaranteeing completeness (allowing you to confirm whether or not you have downloaded all the posts ever created by a user), and preventing timestamp forgery.
SSB has something like this but it requires a user to download another user’s entire post history before being able to see one post. Makes the experience very slow.
Timestamping is already possible using the bitcoin blockchain. No token scam or new blockchain needed
I didn't say decentralised timestamping is required for a social network or any blockchain needed