This should be a standard for all first person games

There are technical reasons to explain why it isn't.

If they gave me 1Euro ( or Dollar or whatever) everythime this was requested in the past TES games I'd be very rich

I really wish for a mod that does this. I was a little disappointed when I found out that they didnt make it in Skyrim.

One major issue - in order for you to be able to see your hands in 1st person, the player's arms need to be placed unnaturally high, causing a problem when you then have to show the connected legs and torso. Think I've only seen one game where the weapon was held at the normal height (one of the Tom Clancy games). I myself would still prefer it, but most people are used to seeing their guns/swords/whatever.

it should be possible eventually. I'm pretty sure the new skeleton system for Oblivion could do it. (Deadly Reflex has it so you can see your legs when kicking enemies)

mostly what you see in a game is with the movement of your eye's and tilt of your head (for 1st person view). to see straight down would mean bending your waist or neck which we don't have control of

Or the legs could be moved in the 1st person skeleton, to be in sight of the Camera.
I assume the problem with my theory, is it would require the animations to be changed. And few people want to do that.
It might have other side-effects that i dont know about, I'm just guessing. It just makes sense to me. Cant see the legs in 1st person? move them so you can lol.