Oh man. Let me tell you, I tried out Bikram Yoga once for about 3 months (yoga in a 90-110 degree room with like 70-80% humidity for 90 minutes) and I've done karate for about 12 years now. I am still amazed at how it seems that once men hit the age of about 55 or so, they just stop trying to be modest and keep covered up. I would be having a conversation with somebody on my way to the showers, and then I'd turn around to be polite and initiate eye contact, and WHAM. Just chilling there naked, letting everything air out. Bro, you have a towel. I would like to focus on our conversation, not trying to do everything in my power to avert my gaze from your old man testicles.
The karate place was at least a little more discreet in that people would usually turn and face the wall so that if you were talking to them, you didn't see anything that would scar you for life. That and it was a quick change there. The yoga studio was like "hey, it was hot as hell in that room. I think I'll just chill here being naked and cooling off". Yes, I'm about to do that too, by walking out into a January evening at 8:30 in a T shirt and driving home with my windows open.
I used to worry about it too, but I'm getting to a point where I don't really care anymore. It's not like people are trying to stare at my junk and judge me for it. Once I came to that conclusion, it was a bit less stressful for me.