I hear that too... way more female subs than male Doms and even though we all think 'he only needs one' the point is that it sounds like he's looking for a relationship that also includes bdsm.
While there are many people who have Dom/mes as well as a separate vanilla partner, someone who wants a sub as more than a play partner wants to find a companion they can talk to and share life experiences with outside the bedroom or the dungeon.
I do agree with Delia that the younger crowd tends to be more vocal in certain areas of the site, as it normally is with technology, and yes emotional maturity matters too as I'm sure the friend of the op has taken into account... some people just don't feel comfortable dating someone a certain numbers of years younger/older than them no matter the emotional maturity of each.
As so many people seem to say, someone will fall in your lap when you aren't looking![]()