Because one should always be cautious with giving out personal info on the Internet. I believe that I first had my profile hidden.
The obvious answer to that is that you can choose to leave out as much or as little info as you wish. Well, thru your profile people also get access to your fan registry, and in that one people might want to state correct information - because they think they have to when they first came here, or because they want to contribute to correct fan statistics.
And, btw, thbdbh.
-Right! So nobody leaves here until I get a slow song right! (David Bowie)