However, I can guess why it isn't common. What you suggest would be labor-intensive, and thus expensive. Some people don't want to pay for the hand-holding. So the gym would have to offer multiple plans: cheap do-it-yourself and expensive hand-holding. My guess is that this has been tried, and the number of customers for the high-end plan is not enough to justify offering it. Alas.
However, I can guess why it isn't common. What you suggest would be labor-intensive, and thus expensive. Some people don't want to pay for the hand-holding. So the gym would have to offer multiple plans: cheap do-it-yourself and expensive hand-holding. My guess is that this has been tried, and the number of customers for the high-end plan is not enough to justify offering it. Alas.