I'm sorry to hear that you don't want to register. I agree that usernames are frequently unnecessary, and for other sites that I've created I avoid them.
However, I think it's useful for this website because you get a profile page with a URL that uses that username. For instance, here is mine:
However, I think it's useful for this website because you get a profile page with a URL that uses that username. For instance, here is mine:
http://curiousreef.com/kday
Sure, and email + alias could work also, but I really wanted people to have their own vanity URL, and this seemed to be the easiest way to do that.