The point isn't so much that there would be a lack of bullets. Just a lack of a way to get bullets. There aren't any more cars/trains/planes, the only way bullets are getting from Factory/Armor X is by some enterprising ballsy dude who has to hack his way through the wasteland with his stash packed onto a brahmin trying to trade bullets for something without getting shot after he hands them over
Point being if someone wants to save resources or doesn't have anything to trade or never even comes into contact with a bullet mercahant they'd be stuck to their own devices. Even besides those points bows do have a most definate stealth advantage over guns. In many situations I'm sure a wasteland loner would prefer to make silent kills rather than alert peole for 5 miles around.
Bottom line F:NV is a RPG. It's a Post-apo RPG. And having bows would definately fit with roles I'd enjoy playing out.
