Changing room showers, under 25's

Hey, i'm 21. I go to the gym about 3 times a week, and swimming twice. I have done for the last few years. I find it pretty normal to use the 'open showers' afterwards. However, i've noticed quiet a few younger guys don't.
I wonder why? If you are under 25 do you? Does age make a differance?
Seems that allot of guys of my generation are scared to be naked infront of other men, we've all got the same bits.. So why??