you ask the question how many entered the hobby as a substitute, supplement or adjunct..or strictly out of curiosity or boredom....

Did you consider that some of us came into the hobby because as soon as we heard about the concept (as young boys) we knew it's what we wanted....

I am 25 and have very limited sexual experience. I can get decent looking girls in the real world if I try, but it is hard work and I am extremely picky. From my point of view, why go after the okay looking girl when I could go for the knockout. Unfortunately I am also very bad socially with women and get extremely nervous. That all adds up to not much success. So I started hobbying a couple of months ago to increase experience and confidence and hopefully eventually be able to have no fear in approaching whatever women I desire in the real world. I don't intend to do this forever. I only want to get to a point where I can build and mantain my own relationships with civialian girls. The other reason is to satisfy that urge to get the best looking girl in the bar. As a hobbyist and can be intimate with whatever girl I desire and can live out any fantasy. Being with a girl way above my level brings the real world back to earth. If I had a happy relationship I wouldn't be anywhere near the hobby. That's just my personal story. And I'm having fun and gaining more confidence with every experience.

convenience.

i have plenty of "friends" ... and enough "little sisters" to start a convent.

like most men, i prefer not to use condoms but i am getting too old and too through with kissing some civvy ass for 3 weeks or more just to maybe get some naked nookie that will try and power trip me and frankly just isnt that good anyway.

i'd rather use the money i'd end up spending anyway on someone who has the skills to overcome the skeet trap and will at least attempt do a good job of making me happy instead of just laying there waiting for me to finish my workout.

the variety is nice, too

I entered the hobby as a supplement to my marriage (I was happily married for 34 years until my wife died last year.) My wife was not interested in swinging (I asked her) and I could not visualize complicating another woman's life with an "affair."

Hobbying has always been a clean, no-strings attached way of having sex with women other than my wife. My attitude toward it has not changed much in 25 years - the women I meet now are as fascinating to me as the women I met 25 years ago.

My frequency has changed up and down over the years, but that was based on my travel schedule (I have never hobbied in any town I lived in.) I have never had misgivings or reservations about it - I enjoy it for what it is.

or restarted I should say. When I was single I would sometimes hobby (not that it was called that)because it was easier than trying to find some civvie girl, the girls are usually better looking than civvies, and you don't need to deal with all the BS that comes with dating girls.
Now that I'm married, I was faithful for a long time, but now she's getting older and losing interest and doesn't seem to understand that my dick still thinks he's 22. So after years of begging, be unfufilled, and pressuring her to do things she doesn't want to. I decided that I needed to go outside the marriage. But since I don't want to end the marriage, a girlfriend is out of the question; that wouldn't be fair to anyone involved.
So, the hobby - beautiful girls (younger and hotter than I could ever get in real life), hot sex (most of these girls will do stuff that would make my wife queasy to think about), and, best of all, NO BS! I want your mouths and pussies, ladies, and that's just about it. I mean, a good conversation after the deed is done is great, but I'm not paying for that, I'm paying for CIM!
Now the problem is stopping again. Running out of cash will help, but I'm pretty sure the wife will notice that. I need to find the balance. A weak experience will help slow you down ("I paid $$$ for THAT?"), but the great ones (Ahhh, Janna) just make you want to get back on the horse.