I think it mostly has to do with the client-server technology of the web today. Once effective technology exists to decentralize key aspects of the platform - hosting, accounts, etc. - you'll see less consolidation in one provider. You'll also see a lot less feudalism when it comes to the power dynamics of users and organizations vs services (like Uber, Facebook, Google, etc.)
There needs to be a protocol to decentralize social the way bitcoin decentralized money.
Disclaimer: I'm working on just such a protocol and reference implementation (http://qbix.com/platform/features/distributed)