It would just give them something else to complain about. But they would also complain if it worked as it would IRL because "it's a game and they should be able to" so to be honest it's probably better just to leave it out!
Don't get me wrong, I don't think you should be able to fire a bow underwater in Skyrim. In fact, I think underwater combat shouldn't go any further than daggers and unarmed.
I don't understand WHY people feel that underwater combat is needed. First of all, the water would slow down all movement, and the fish would be too fast, which would make underwater combat stupid. On top of that, the only enemy you would actually be fighting would be slaughterfish, so the whole feature would be completely unnecessary.
A fish is only fast because it's adapted to being in water. Surely if an Argonian can breath underwater, then it has adapeted to being in the water. If they've adapted to being in the water, it makes sense that they would be able to fight underwater, as well. Even so, knives can be used underwater quite effectively; both as tools and weapons.