Because it's your identity. Login systems have moved away from the 'username' concept that we used to use, because it was another thing we could forget. Email a

Because it's your identity. Login systems have moved away from the 'username' concept that we used to use, because it was another thing we could forget. Email addresses are inherently unique and allow identifying a person for support calls or login or whatever. I'm not saying this is necessarily a good thing, but this is how things work and I don't have a better suggestion.