This has been occurring to me for a while and is now really sinking in. My gym is very much like adults doing parallel play. That type of play that very young children do when they're able to play with toys in the presence of other kids but don't want to interact with them.
Now that's not entirely fair. People do interact with each other esp if the already know each other and I know some folks in class, but it's not the default. I'm so used to dog and team sports where you have to interact, and it's part of the fun. I think I'm feeling this acutely right now because I took a month off to heal from some tendonitis and I hadn't been doing the RPM class as much any way. Now that should be nothing for regulars, but it's just long enough for some shifting around and the people I usually see there aren't there, and I never knew them that well. Compare that to dog agility where I know people very well esp. if they're in a class of mine or in my club. Even in herding or obedience I have plenty of time to talk to people, and I used to that and miss it.
Now my gym membership is due and I think I need a break from it, but it's a great way to get wintertime exercise. However it cuts into my dog walking time and I don't like that and I can run with Trek at noon if I like. Not to mention (that's a weird phrase as I'm about to mention it), it's expensive. If you have no other way to get exercise it's an excellent choice, but I think I can keep up with it and there are running, biking, hiking clubs a plenty so I'd get my social outlet too.) And I can't help but look at the price and think that's 11 lift tickets or 1/2 a bike. I'm also at risk of my depression coming back if I don't exercise, but I actually feel more depressed after the last two gym visits, so maybe it's not helping with that at all. I like the dog walks as I spend the a lot of the time talking to the dog, and they actually listen too. I think they're easily amused. I also talk to people whose houses I often pass by on the walk.
Though I will certainly miss the over the top nature of the RPM class. I just love it. I think I have to wait long enough to miss it.