Nothing to do with the mechanics of the game, more to do with me.
Whenever I build an interesting character with an interesting weapon, I want a copy of that weapon. Usually I tend towards practical weapons that actually work, and blades are a good bit cheaper than guns, but with blades as a collection thing it's much easier to find massive numbers of them. With guns, I can at least go "Ok, I need a gun to fill this role, can't buy anything else until I've filled all roles I still need guns for". Since the entire purpose behind everything beyond one good sturdy combat knife is "because why not/cool", there's no semblance of need involved. Just want. Lots of want.
At the moment, I want a second SOG Tactical tomahawk (Highly recommended, by the way. Works great, feels great), because the FancyZerker wields a pair of axes. More on that in some other post.
I also want pretty much every sword-machete made by Cold Steel. And their Grosse Messer, and Basket Hilt Broadsword. And training versions from them or other makers for everything. And more people to train with.
Seriously, every time I use a particular class of weapon in a game, I want one.
At least I'll have stuff to decorate my Dwarven fortress with when I build it...
(anyone can make an underground house, but they're usually ugly as sin, which is just wasted potential!)