You just did tell us.
(More generally, you don't need to because people can assume it by default. You don't have to worry about getting a fist in the face when you chat up a member of the opposite sex, for example.)
Plus, since you're happily posting as Anonymous Coward, I think it's kind of obvious that you don't see the point in having any kind of profile! But not everyone is like that, straight, bi or gay.