That's because you haven't made a post yet!
The board is set to only list members in the membership list after they make a minimum of one post. Why? Primarily because it helps prevent spam registrations where the spammer or spambot registers and tries to post a link to a website, which may have embedded malicious code, host pornography, be a spoof 'phishing' site trying to get your passwords, financial information, etc.
Most spammers and spambots register and try to insert a web link into their profile as their sole goal, and then never will return and don't actually make any posts, so this keeps a potentially risky website link from being visible -- or worse, clicked on by board members.
The spam protections on the board are already quite rigorous -- that's why you are asked an extra spelling question on registration, and then, why you need to return your validation email for me to manually activate your account. So this is just an extra, final layer of protection.
A second reason is that I don't think there's much point in showing member profiles for people who aren't minimally active as no one would be likely to look at their profile anyway. This way, the members who appear in the profile listings are the ones who are or have been active members.