The real issue is the brass tacks. Who can afford to run their own private servers, or pay for data throughput for synching. Not to mention the enormous waste of energy and resources due to duplicated posts kept across millions of peer to peer networks. Convenience is King as usual, and places like Facebook have the motivation and ability to monetize and optimize.

The idea of private data atolls in the day of free services is a luxury and they are exploiting that facet. Cloud services like Gcloud, AWS, etc reflect this from their premium pricing.