NSFW How's it hangin'?

Ok, I’m having a perverted curiosity moment here. Please excuse…
It’s a little surprising that I could reach my present age (don’t ask) and still have to wonder about this, but so it is. I guess it’s because it falls into the category of things you’re not supposed to think about if you’re a “nice” girl….(well, I am a nice girl, but I’m plenty naughty too.)
Inspired by my subway trip home today:
I was staring ahead of me and this guy who was standing over me, well, I couldn’t help but notice his crotch because it was right in my face.His cock seemed to be hanging awfully low yet off to one side….and, I guess it was a little on the large side, but not huge or anything.Hmmm, I thought to myself,why’s it hangin’ so low? I mean, if he had briefs on they would hug that sucker tight to his torso, wouldn’t they? But if he has boxers on wouldn’t it just hang straight down between his legs. Is there some sort of penis calculus involved determined by tightness of underwear + tightness of pants + size of one’s member?

So guys (and girls if you want to have your 2 cents) how does that underwear thing work when it comes to keeping you all snug and tucked in or all loose and dangling? Elaborate at will.

Sorry in advance if this is a stupid question. Inquiring minds, you know, want to know…