In college and early post-college years, pretty much saw all of my male friends naked (e.g., in dorms, fraternity, apartment roommates, etc.). Pretty much if you had to take a shower or change clothes, we'd strip down without really thinking about it if people were hanging out in someone's room BS-ing or in showers in the morning or after going to the gym. Now I have different kinds of friendships, the non-seeing-your-junk kind of friendships (which is totally fine with me). Saw some female friends naked, too (e.g., in random one-off hook-ups and skinny dipping once on spring break).
I actually really miss having those kind of close male friendships, and not for the nudity, but for the friendship aspect of it.