In my experience, the clubs cater to a niche. They’re effectively a kink in and of themselves and there’s a very explicit innuendo that sex is to be had on premise. Nude beaches on the other hand are a casual exploration of being clotheless. And while sexuality plays a part, it is not the focus of the experience and is often generally discouraged. I think nude beaches are cultural and thus more prone to the ebb and flow of said culture. Swingers clubs are a fetish and will exist regardless of culture as long as there are people with the kink.

Haven't seen stats but it sure feels like ENM and poly are cannibalizing the alternative sexuality world and reducing the popularity of swinging. Which IMO is for heterosexual couples at least a bit of a loss, as swinging seems to favor longer lasting and less self-imploding relationships.

Photography is usually explicitly forbidden in these spaces.