Why do teens scratch their balls?

Ok so I was at rookie band camp a couple of weeks ago. In are trumpet group, I met the new freshmen. As we marched outside, teaching them, I couldn't help but notice one guy that kept sticking his hand in his pants. There were only 3 girls around and they were nowhere in his line of sight. He just casually stuck his hand in his pants grabbing his sac. Why do guys do that? (and no it's not b/c they itch, I'm a guy and my balls have never itched that much that I had to scratch in public) But this kid that I saw, I'm 100% sure he got the itch, but he kept doing it? I can't comprehend it haha