I changed with other boys to go swimming and stuff from a pretty young age - don't really remember when it started. Changed clothes for PE class starting in 7th grade. First shower was after a lacrosse game in 8th grade - only a handful of us got naked, the rest showered with their underwear...
No one's making you buy them, guys. Like I said in the original post, if you don't want them, I'm happy to keep them. I love them, so $50 is how much it would take to get me to part with one. You are all welcome to set whatever price you want for any jocks you sell.