I feel like it's a form of opportunity cost that creates an imperials debt. Decentralization, and even more so all the motivations that lead developers down the path of decentralization, has nothing to do with making a good social network. It's like all the solar-powered cars... a cute idea, but no one ever (ever) buys a car for fuel efficiency. You buy a car to travel, to carry things. So the solar cars are cute, but they fail at everything a car is supposed to do. You can't possibly improve on something unless you start by implementing the thing.