It would probably be more useful in the early game or for stealth characters who'd rather fashion their own scrap arrows instead of finding ammunition, or for having poisoned arrows a la the Dart Gun, or maybe even non-lethal approaches like sleep darts.
Not to mention the badass factor of hunting in the wasteland with a home-made scrap bow/crossbow. The "why bother if it's useless" argument can be made for anything that isn't the "Ultima Weapon", and I'd rather Fallout 4 have an item progression that allowed weaker items to become viable in the lategame. I hate when an RPG has equipment progression that gets less and less diverse as the items get better.