I don't think that's the case. I know a ton of people who went from seeing movies almost never to seeing them several times a month. They had the opposite problem of a gym - having a moviepass membership available actively changed people's moviegoing behavior on a wide scale.
Gyms also don't pay a per-visit overhead cost for a given member.
This is more or less why AMC can successfully offer A-List.
If 100 people use moviepass, moviepass loses 100*$X
If 100 people use a gym membership. The gym loses $0. And maybe a few people cancel because it's too crowded (or better yet, don't cancel but stop coming)
Wouldn't you consider that a per-visit cost?
A customer with a gym pays a monthly rate... That rate is paid even if they use it. The running cost of the gym remains the same whether or not someone comes to the gym.
This comparison, then, doesn't make sense. MoviePass is paying directly each time a customer uses the service. While both services are better off with people simply giving their money for something they don't use, only MoviePass actually LOSES money if people are using the service. The gym, on the other hand, doesn't.