There are dozens of reasons, any one of which would be enough to make me stop using centralized exchanges. And yet people keep giving their money to these companies which treat them so poorly. And so the cycle continues.
The sad thing is that convenience and user friendliness is considered higher than everything else. And even for me, to be honest, I choose convenience and ease of use rather than a secure p2p trading that still comes with its own risks. I comprehend at least the benefits of trying to choose something that is not a CEX but also for most people, choosing p2p or something decentralized could be more dangerous (like all those guys who get scammed on localbitcoins).
At the end of the day people are willing to pay for convenience and "feeling of safety". This is the problem non-CEX need to overcome.