I can only answer for myself, others may have different reasons.

Way back when I joined this site a couple of years ago, I was single and looking for a relationship. During my time on this site, I came to love reading and sometimes posting in the forums.

Then, last October I met someone (not from this site) who I did want to have a committed relationship with. For awhile I simply changed my profile to have a picture of the two of us and to read something to the effect of "I am no longer looking and only keep this profile active because I love the forums on this site".

Sadly, that didn't stop people from winking and emailing me, and assuming I was looking to cheat, etc. So, I simply hid my profile. Allows mw to participate in the forums, but is pretty clear about the fact I am not looking for anything more than I have.

Well in my case, I have hidden my profile because I am in a wonderful relationship with a man from this site, but I still enjoy coming over from time to time to read the forums and blogs.