Well... how would the platforms sustain themselves if they dole out "special privileges" to too many users?

They wouldn't. Platforms will take a small percentage of the posts and the 'fees' in sats that people pay to post... and use them to fund the platform.

As opposed to doing it today through advertising/data collection.

How can you "know" that people aren't bots today? Or that their posts don't have 'special privileges' on Twatter?