I'll tell you why I wear briefs in the shower in public locker rooms.
I'm a very easily aroused 43 year old man (by guys, mostly) and a lot of times I wear an unlubed condom under tight briefs to keep my precome from soaking my crotch, especially when when I'm at the gym .
Beside the fact that working out makes me feel masculine and horny, I see quite a few guys at the gym that make my dick hard and leaky, and when I'm in public, how horny I am is my private business. It's just part of my being a man.
So, wearing a rubber to catch my dick lube is a private thing I do being a man and that means keeping my briefs on in the shower at the gym. I kind of suspect that I'm not the only guy out there who keeps his pecker wrapped so there's no mess in his shorts. I'm pretty sure that's why SOME of these briefs-in-the-shower dudes keep them on. As someone earlier pointed out, men like their privacy.
No way will I get undressed in front of other guys, If the pouch of my briefs is soaked. And only a creepy exhibitionist would walk around nude with a condom on. Besides, I believe that could be called "lewd conduct".
Of course it gets me off that what's under my briefs is a little more private and sexual that some other guys, but I think you guys that miss seeing a lot of naked cock in locker rooms should discover how hot it is to see a guy with a nice, tightly packed bulge in the shower, his wet briefs clinging. Imagination is a way bigger turn on than furtively ogling another man's plain nakedness.
Thanks for reading this. I'll step down from my soapbox now. My rod needs a good pounding.