If I'm not misunderstanding something, most cryptocurrencies aim to be "digital cash." I.e., fungible and anonymous. One bitcoin is like any other bitcoin, apart from an identifying number. Much like a banknote. They can be tracked, but only with difficulty. You can say that a particular one passed from A to B but not know any of the intermediate steps. Some are more anonymous and some are less anonymous.
It doesn't seem to me that cryptocurrencies are a natural fit to identity. Or that blockchain technology in general is, either. It hardly seems worth the effort of bodgeing stuff onto a blockchain to allow it to deal with identities. But maybe I'm missing something.