Why do so many people seem so hesitant to...

Why are so many people so hesitant to bare it all? To get naked. Changing in the locker room, gym showers, swimming, etc. This generation just seems so much more... uptight about their bodies. Why do you think that is? Be as specific as possible. Try not to give me a one sentence answer, I actually want to read what people think, not another "Just 'cus"