Maybe because they're so ashamed of their horrible spelling?
That and this forum may include anime, software, movies, music, etc. that is licensed / copyright / trademarked. Not to mention Hentai and Doujin, information which some people would not like others to know they've seen.
Other senseless but interesting to think about questions: (You're welcome to post new threads with these as I'll probably post 'em eventually anyway. Please only one at a time so the topics can be discussed thoroughly.)
Why do stay in your house and lock your door?
Why aren't all the doors and walls of your bathroom made of completely clear glass?
Why do you wear clothes (especially when it's so hot)?
Why don't guys to this
to all girls they meet?
Why do you like hentai so much?
For that matter, why do you like anime so much?
Is it hard to live and easy to die, or easy to live and hard to die, and why?
etc...