For me the incentive is being able to own an identity that nobody can take away from me. And the assumption is that services will support this type of identity, so I don't have to make accounts on other systems that people can take away and now I've lost all access to any data I had.

I think what you are looking for is something like Mastodon or related activity-pub service. You can run your own instance and nobody can take that away from you. No need to drag a blockchain into it - just host whatever services you need.