I don't really know what it is with males touching their genitals. It is something very common among them, and frankly speaking, I am not left out of the whole thing. I think it one of those things we do habitually without knowing about it. I don't there's a guy that doesn't like touching his genitals involuntarily, but it seems there are those, there is worst than the others.
I have a friend that, he can't stay for one minute without playing with his genitals, and he does this both in private and in public. Anytime we are together, I will be monitoring him as he constantly touches his genitals. And find it difficult to confront him and tell him what he's doing is inappropriate.
To make matter worst, that same hand he is using for it would be the same hand he would like to shake people with. I just think there is psychological aspect to this phenomenon of guys touching their genitals, which explanation is yet be known.