Actually PP, 95% of the offenders are old men.
They do not hesitate to throw one leg up on the bench and tell you a story from the old days with their wrinkled sausage out and about.... I'm sure old women are probably the same way with their old floppy boobs, right?
This is also the reason I prefer to change before I go to the gym, if possible, and I'd also rather not shower in a place where you have a 75% chance of getting athletes foot. Just like Raina said, its better to shower at your house.