Well, that's palpably incorrect. You clearly get both for the same action.
In Skyrim, it will often happen that an arrow fired dead on target will miss because the target moved unexpectedly. (I'm not talking about the infamous "ninja dodge" effect, but simply - movement, that turns out to be exceptionally well timed from the target's point of view.) It's particularly frustrating when the shot triggers a killcam, showing that even the game itself thought that was a perfect shot.
And Skyrim has good enough graphics and animation that you can see what happens. What it doesn't have, however, is any attempt to simulate the sheer difficulty of aiming a shot on target. You focus your convenient crosshairs, hold the shot for as long as you want, then let fly.
Shooting a bow is nothing like that, even making allowance for Skyrim's extremely elastic ideas of "simulation". There are no sights, to start with. Because you're exerting all the strength of your arms, it's hard to draw any kind of bead on your target - that's why archery needs practice, lots of it. And even for an expert, holding a bow fully drawn requires an immense amount of energy, and will quickly tire the archer. (It's not at all good for the bow, either.)
And then there's wind, and precipitation, variability in the tension and balance of the weapon...
I have no experience with swinging a sword in melee, but I imagine there are similar effects at play there.
The act of aiming the weapon does no more than designate the target. Whether you actually hit it or not is a whole different question. There are games that try much harder to simulate the physical difficulties (Kingdom Come: Deliverance springs to mind), but the trouble with this approach is that player skill rapidly starts to upstage character skill. On the whole, I think a weighted die roll is a pretty good way to capture all of this stuff, which also accounts for why tabletop games have pretty much always worked this way.