Some guys do it for the brag value, those arent usually the sort ive met tho.
Mostly its guys who just REALLY like the way a particular rifle, shotgun, pistol looks and feels. On the top end a well fitted custom rifle dosent have to be fancy, but for some folks spending the extra 2-5k on getting the exact wood, finish, and metal work they want makes them happy, and it makes ME happy to see those firearms being used.
I dont generally like high gloss on top end wood. I prefer a nicely finished oil rubbed stock, but with the correct checkering/engraving and metal work, high gloss can completely change the dynamic of the stock/firearm.
I usually have no reason to hunt, other than its very much a part of who I am, so my hunting guns arent tools exactly, they are an extension of that part of my personality. Carrying a beautiful piece of equipment, can and HAS, made a day out and about much more pleasant.
Im also broke enough, and live in a harsh enough environment that Ive only owned one very nice rifle, which I sold to fund a new car. I dont miss that gun, because ill buy another one of similar quality when I can afford to.
I spend a lot more time tinkering, and modifying than i do shooting or hunting these days tho, so Im happy with guns that are cheaper and rougher.
Im also a rifle guy, I shoot shotguns, and handguns, but they dont really feel like "MINE", so im less likely to want a fancy shotgun or handgun.