Isn't it tiring? When you can click and login, you choose to fill out 3-4 fields. About the ownership of your data,what if the app asks you for the permission of fetching only basic information nothing else?
Even if the app asks only to fetch basic information, I think that I shouldn't go through them (Facebook, Google, Twitter) to assert my identity, since I don't pay any of these companies for this service, I can't trust them to keep my best interests in mind.
I feel that there should be a way for me to be my own identity provider, and email has been the closest I've got to it.