I watch people who wear their underwear into the shower, or shorts, or hide behind towels, and I wonder what it's like to not be comfortable with yourself. I'm a big guy, BTW - not my prior 365, but down to about 235 (with a significant amount of muscle tissue mind you). I've worked at it, and I have no reason to be embarrassed.
It’s not about shame, it’s about courtesy. You have no reason to be embarrassed but I still don’t want to see your naked body.
I actually don’t have a problem with nudity in media but it should be people’s choice to NOT have to see it in the same way that you can choose not to see violent media. That doesn’t mean it shouldn’t exist at all.
I'm not swinging my junk around, I'm not sitting nude on public seating ... I'd never wear a towel to the shower - I'm sweaty - why would I want to put my sweat on the thing that is going to be used on me after I'm clean? I find I only bother wearing the towel back from the shower to dry my legs, and that's only on occasion (or if the change room is cold). Beyond that, sorry, but if you look at me while I'm changing, yer likely gonna see a naked guy.

So here's a question for you, Lordnine, and think about it first :
courtesy to what, exactly? What are you doing wrong in someone else's eyes by being naked in the shower or a change room? What form of courtesy is it, where another persons opinion of you overrules your own "sensibilities" in being naked in a place thusly designed for said state and with clear functional intent? Courtesy to children who have no interest in you more than they do an interesting tree, or bug, or rock they've seen? Courtesy to people who feel the need to cover themselves up, and expect others around them to do the same? Why is your disinterest in seeing naked people, while in a place expressly designed for people to be naked, more important than my need to get clean? You chose where you look. I've seen dozens of men in a day, and no penises, though they were all naked. I don't have any interest in it, so if you just relax about it, it becomes moot.