This is made me laugh because my partner and my two boys do these. And I couldn't find any reason why they keep touching their genitals. Even my little ones are just innocent, but they discovered early to touch their genitals. I know they are innocent, maybe because they it more interesting than the other parts of their body. About my partner, he will just scratch it if its itchy that was his reason. But for my two littles perhaps not the same reason as their father has. The genitals are most interesting part of human body, maybe because it gives you a different feeling and for not intents as science may explained about it. I could not explain further more than that because I don't want to say something here that against any rule. But as far as I'm concerns, its part if human body.