No, I never find the need to. I've noticed it's very common around straight guys, especially if they're wearing athletic shorts. I find it kind of a turn on, but I really don't see why they need to do it so much.
I would say that it's only a need if they're wearing snug underwear with their athletic shorts, like briefs or boxerbriefs. I live in gym shorts outside of work and always wear boxers with them. Nothing gets pinched, and I rarely need to adjust. The other possibility is that they just like to touch themselves and make others aware of the dick in their shorts. I've seen guys in the gym doing this, and I like it when I see it.I've noticed it's very common around straight guys, especially if they're wearing athletic shorts. I find it kind of a turn on, but I really don't see why they need to do it so much.