38 myself... learned to fly at 30.
I would agree:
1. those 25-45 too busy having and paying for children;
2. social life tends to revolve around work and/or children, not clubs;
3. when I do get out it's for a limited time: no time to hang around and chat at the club, just in, fly, home.
I certainly plan to spend more time flying when I have more money and fewer kids at home...
Tim