Actually, now that I think of it, we could probably name a lot of other services that rely on this business model and do a thought experiment like the gym one.
An airline for example; now everyone actually caches their flight because Google's self-driving cars always make it on time, and then they demand that Google stops bringing passengers on time?
Or a buffet restaurant, since now everyone goes to the gym, they can actually eat a lot more, thus restaurants complain about, either the gym or the pill maker?
I don't know, it would be a strange world to live in if this happened in other industries. Maybe prices would rise too much?