Because Uber and Lyft extract much of the value from each ride. If Uber or Lyft were a blockchain-based peer-to-peer protocol with its own utility token, the users and the drivers could easily benefit from the value capture. For what it's worth I think the decentralized Uber example is a bit contrived and that these applications are more complex than people realize. However, ultimately that's what I see in Decentralized Finance (DeFi) apps: I see loans being made via a smart contract that automates away much of the middle man infrastructure of the banking system. And therefore I as a depositor can get a higher yield than I can at a regular bank because the only thing between me and the borrower is code.

I'm not convinced that centralized is better in every way for the more complex examples, however. I just think the tooling and distribution aren't quite there yet. And sometimes it will take a rethink of the existing application. For example, Uniswap is a great decentralized exchange, but the constant product architecture it used to achieve its result is much different than the standard order book architecture that centralized exchanges use.