The YMCA I belonged to was in a really old building that had been a mansion/hospital/nursing home before it was turned into the Y. The 18 and over men's locker room was small, weirdly laid out with the lockers in different rooms and the wet area (showers, steam room, sauna and whirlpool) in a central spot and the workout room on the other side of the wet area.
The only place that clothes were required was the workout area. And even then, I saw a couple of older guys would go in there completely naked to get a drink form the water fountain. But those guys walked around everywhere in the locker room completely naked. A few guys would wear their underwear/swimsuits in the locker room, but that was really rare. The swimming pool was connected to the all ages men's locker room and it was difficult to get to the over 18 locker room from the pool, if you didn't know the code to unlock the door between the locker rooms, you would have to walk all the way around the lobby. A majority of the men would wear their towels, but would be naked for the shower or whirlpool areas but wear their towel into the steam room and sauna. And a few of us, me included, would walk around naked everywhere but the workout area. I never took my towel into the steam room and I would take it into the sauna with me but fold it up and use it as a seat.
I stopped going to the Y when the management team announced that they were working really hard on getting a new building. The building was going to be on the edge of town, but really far away from where I was living at the time. In order to save money, they stopped taking care of the steam room, it was constantly breaking down. And then the whirlpool broke down and they said they refused to have it fixed. The cleaning in the over 18 locker room became very sporadic and it started to smell really bad in the locker room. That is when I dropped my membership. It took them a few months before they started construction on the new building. After it opened, the closed down the old Y. A few years later, they demolished the building. I heard that the wet areas at the new Y were all co-ed. You could no longer be naked.