I'm 22 and about to get my 686+ that I got in a trade for a red dot. I use to shoot Cowboy Action when I was younger but fell out of that due to work, so I do appreciate the old stuff. I also have an old police Model 10 that is well loved and used. Overall, I really am a firearms enthusiast and enjoy all firearms, from muzzle loaders to my everyday carry Glock 19 that has a RMR, KKM bbl and comp, and X300U.
I think a lot of posters have already hit the mark as to why you're not seeing older guns in the hands of younger folks, the guns themselves were produced so long ago, spare parts are getting harder to find, and the rising cost due to appreciation. Like one poster said, he bought them new, or not too old, when he purchased them. Much like old Model A's or T's, while the decades go buy they'll be horded up or scraped as they reach their rusted end, people who don't know their worth do whatever with them, or enter another large collection of someone who does know their worth.
I suppose you could correlate the trend of older folks and their collections or pieces much like their homeowner status. Younger ones are in the cities due to college or their job and are currently facing high-rent, low-paying (probably janky Amazon or Star*ucks jobs) jobs, and disproportionately higher home prices. With lower prices, even with inflation, of homes and firearms, they were acquired back then and are still being held onto, or sold for good profit. I know one old guy who passed and had around 60 benchrest guns, unfortunately I never found out what big firm or store bought all of them from the dimwit son.
I would say that overall, a move towards newer technology such as polymer and autoloaders has given the sheer might of industrial production to the Glocks and ARs of the world. There's quite a few of my peer shooting buddies who all have old guns, from Belgian Auto-5's to Mauser C96's, and they love and cherrish them just as much.