On the backs of the hands, sure... but plating over the whole hands (like fingers) wouldn't make sense unless the only weapon you have is a club. Gauntlet-size fingers couldn't fit in the trigger area of a gun...
Agreed. Hand armouring isn't that important as the risks of getting hit on the hands in a gunfight are far smaller than in a swordfight, so massive gauntlet-like protection is a minor issue in comparison.
The fact that there are still Super Sledge wielding maniacs in the Fallout 3 universe is just a sideshow, as you'd typically have armours specialized to the purpose or you wouldn't bring a sledgehammer to a gunfight in the first place if you look at it from a realism point of view - none of the armours in Fallout 3 are designed for heavy melee combat when it comes to protection and articulation, but are either more rag-tag improv suits or decidedly designed as mobile gun platforms (with the exception of combat armour perhaps, but that design in itself doesn't make sense. Who's ever heard of riot gear without sleeves?).
In any case, whatever looks good should be used as it's not an issue whether it's realistic or not, as long as it looks credible. No-one has any right to flaunt the realism flag when the player can get weapons that can spew green blobs of plasma, lasers that evaporate people to dust and huge super mutant friends with a horrible wardrobe.