I go to the Manor Street swimming baths in Chelsea. There are no individual changing rooms so everyone changes in public, individual men as well as crowds of school boys, mostly private schoolboys. Everyone has to change in the same open area.
Here's the thing. Most of the men and I mean a distinct majority, do not change from clothes to swim suit and back quickly or surreptitiously but rather pointedly take time off to parade around naked, usually talking loudly and animatedly to each other in poses that say, 'I'm so used to being naked in public that I don't notice that I'm doing it now'.
This fairly shrieks at you but the funny things is that they do it more when there's kids about.
Now if they were all universally well endowed there might be an obvious motive - but they are mostly not...and I don't think its latent paedophilia, there's just too many of them doing this, so why do they do it...?