Various ways.
I have and desire guns that are purely functional. Gunpowder powered toasters. Nothing more, nothing less. Tools, if you will. (G19, AR Carbine, Rem 870).
I have guns because I was drawn to their historical or mechanical attributes. They are in nice condition and well maintained shooters. No safe queens. No engraved, ivory-handled sillyness. Just good historic wood and steel. (i.e. Colt Woodsman, Detective Special, Winchester 52, C&R stuff, etc, etc.)
I have and desire other guns that are blend a little bit of both. (I.e. Good BHP, 1911, Krinkov, etc.)
Some folks like to buy guns that are unique or that look badass. I have very little use for goofy one-offs, or silly production guns like desert eagles, serbu shorties, Calico, Feather, etc, etc. Some are just investments in hopes & dreams like the SCAR and ACR.
A .22LR upper seems to be very functional. If used for training, I'd look at adapters rather than uppers. No need for that much accuracy. Much cheaper. And equally functional.