I agree with all the posts. I myself am facing the decision of where my horse career is going after I go to college. I have always planned on medical school, but new opportunities have come up for me to train horses as a career. Do I want to live where I do currently forever? Hell no. Do I want to have horses in my life until I die? Absolutely. Do I want to practice medicine and save lives? Yes, I've always wanted to be a surgeon. My parents have provided me with a fund (bless them) so that in addition to the college money they have been saving for me, I have a little saved money to help out with the cost of keeping Drummer while in college, and it gives me a couple more years to figure out exactly what I am going to do with my life.
Bottom line, don't judge anyone at face value. Just because they quit riding to move on to better things (or not..) doesn't necessarily make them better or worse, but you should probably just give them the benefit of the doubt. And also, just because you love something so dearly and you revolve your life around it (yes , I do as well, I'm out there after school for hours, even while taking 3 AP and all honors, I choose horses over sleeping and everyday, which I feel is the pinnacle of obsession) doesn't mean that its so amazing that everyone else doesn't do the same. I feel that actually the problem you should be looking at is why it bothers you so much, rather than why those people have stopped riding.