it can be true that most visitors will fit within 15 visits AND that the limit will change things. Just saying there is a limit will make a lot of people think about it more, a lot of people who probably use ~10 visits/year will now sometimes skip the club even if they aren't going to run out because they don't want to "risk it".

also even if everyone knows exactly how much they are going to consume and the "vast" majority will not use all 15 visits, and that ONLY the people overconsuming change their behaivor, this can still have a very significant effect - the overconsumers are more likely to be present on any given day (since they travel more), and you usually don't need to make a massive reduction to fix overcrowding situations - e.g. the difference between a road "at capacity" where traffic is flowing as designed and a huge traffic jam can be just a few cars.