I'm not sure what you mean. My username is the one I use to log in. And the @handle part of the character@handle name.
Mine isn't and I think it was not even possible to pick the same one (it's been more than 2 years, so I can'T really be sure).
the reason for that is security, so someone can't simply pick up your name in zone chat or something and effectively guess your password to rob you clean.
And it's not just virtual stuff.
Imagine someone hacking into your account and buying a 1000 master keys which he then transfers into his account through 2 or 3 fleet banks or the exchange and then sells them for a small fortune (a real one).
And you are broke in real life...