My wife chose this position because, when her trainer (the late-60s guy) got promoted to be supervisor of all of the trainers, he told my wife "Hey, let me know when you've got that certification, because I was talking to Annie (his boss) about you, and we both agreed that you'd be great at this. But don't take too long to get it, because we can't wait forever."
She was flattered, the place is convenient (by far the closest gym to our house, and our kids' school), and after having been out of the workforce for 20 years, she frankly didn't feel like she was playing with a whole lot of chips, kwim.
But I'm quibbling with you, because I think she chose to WORK OUT AT this gym -- and hang out with these people -- in large part because of the youthful way it makes her feel. She definitely enjoys the "hot mom" role, and the attention she receives.