I would like to see primitive weapons more, because there should NOT be such a bounty of ammunition lying around.
For game-play purposes, of course, it's made MUCH more common than it actually would be; A real post-apocalyptic scenario would be like Mad Max: A shotgun with a handful of shells, and half of them are duds.
And ALL of the pre-war ammunition has been laying there for TWO HUNDRED YEARS by the events of NV; It's not going to fire.
Factions like the Gun Runners and the NCR clearly produce their own ammo, but that shouldn't make bullets easy to find for the good people of Goodsprings.
To be more realistic, ammunition should be rare and expensive. And if that were the case, one would certainly expect to see crossbows made of car parts and the like.
weeks making a bow and a few dozen arrows and years learning how to use them
Actually, the benefit of bows and arrows would be how easily and quickly they can be made and used. They ARE simple tools; it's not difficult AT ALL to make them or learn to use them effectively, especially in contrast to the complexity of firearms.
Honestly, most firearms would not even work after sitting for a month in the wasteland. They are complicated, delicate machines for the most part; it takes a relatively large amount of knowledge to maintain and utilize them.