A reader writes:
There's another important angle to this topic: basic sanitation. I can't tell you how many times I have seen a naked old man sitting his bare ass on a locker room bench – no towel between bench and ass. There is both a personal and a social problem with this. Doesn't the old man worry about what was on that bench before he sat his bare ass down? And does he even consider the people who will use that bench after him? Even if the next person uses a towel, or just puts his bag on the bench, now he has old-man-ass-and-balls all over his stuff!
Another also mentions sanitation:
I was a competitive swimmer growing up, and I always heard that men used to work out nude, since pools were gender segregated. I'd never thought much of it, but your thread has inspired me to look into this a bit. Wikipedia's entry on "Nude Swimming" verifies what I'd heard:
Before the YMCA began to admit females in the early 1960s, swimming trunks were not even allowed in the pools,[5] and high school swimming classes for boys sometimes had similar policies, citing the impracticality of providing and maintaining sanitary swimming gear and clogging swimming pools' filtration systems with lint fibers from the swimsuits.
A far more dangerous threat:
Since I have an occupational hazard of working in a hospital, I just recently read a really interesting book, Superbug: The Fatal Menace of MRSA (by Maryn McKenna), and it had a chapter on how the "modesty" effect, even among high school athletes, means that hardly ANYONE is using the shower facilities at school. The kids are (hopefully) taking a shower at home, but sometimes much later after their workouts/training/games. This delay has contributed to bacteria staying on the skin longer and having the opportunity to infect even very minor skin abrasions. In some rare cases this can lead to death. (And lack of "practice" showering in high school carries over to college and professional teams that have had MRSA outbreaks)
I hated showering after gym class, but in the '80s, most of us still HAD TO take a quick bird bath. Now, students don't use the showers at all, even on the football and wrestling teams. So relatively minor changes in cultural norms for teenage "modesty" can have unintended consequences later, leading to even healthy kids getting community-acquired staph bacteria resistant to most antibiotics. (MRSA kills more people than AIDS in the US.) So there is every good reason to hit the showers!