LoL--I have an ancient ThinkPad Tablet running Win95Tablet becuase there are some equally out-of-date software that will only run on that OS. (And I had a pen plotter that only had Win95 drivers--gotta love "sneakernet" . . . )
So, that set up is not quite like owning a Volcanic--it's more like owning a Dreyse; you can still use it, you just have to do all the steps by hand.
Was gabbing on this topic with some cartridge collecting friends--and really, the number of cartridges out there is immense. Far larger than can be seen at the average Academy, or even a dusty, old, LGS. And, basing trends from inferences off online fora is less-than ideal, too.
So, really, the only truly obsolete rounds are the ones that just cannot be produced anymore. Volcanics, trounds, pinfires, and the like. A person could even load up 45schofield if they wanted. Ok, so .600nitro express could be hard to find for components.