Neobr10: No one keeps old PCs around (or at least the majority doesn't).
Those who are still interested in running their older PC games, and which have not found a good way to play them all in their new system, do. Just like they do with their old consoles. The only reason to get rid of the old PCs is either that they eventually break down (just like old consoles do, e.g. I have a broken first gen Playstation still on my closet I think), or to free some room.
While I prefer playing old PC games (and why not also old console games too) on newer PCs with emulators and virtual machines, even I've now accumulated several retro-PCs. They are:
- Compaq DeskPro (runs Win98SE (and DOS): Pentium 133MHz, 128MB RAM, 3Dfx Voodoo 1, Soundblaster16, Roland SCC-1 + CM-32L). I actually acquired this quite recently, and set it up mainly to find a home for my old Voodoo 1, Roland SCC-1 and CM-32L units which had been disconnected for years.
- Some 1.66GHz 32bit single-core AMD machine with ATI Radeon X800 etc., runs Win98SE and XP.
- IBM ThinkPad T41 laptop, runs both XP and Win98SE: I think this is actually my most often used retro-PC, even finished Heavy Gear (on Win98SE) on it.
- One old Dell laptop from the same era as the T41, but for now I'm running just Linux Mint on it. I might try to install Win98SE on it at some point.
The more modern gaming PCs I have are my work laptop (Lenovo T400), and the ASUS G75VW laptop.
I think the first two retro desktops are pretty redundant for me (as well as the Dell laptop), I could probably play 99.99% of my old games on the T41, T400 and G75VW laptops (emulation or not). But since I've been able to cram all that PC hardware nicely into one IKEA computer corner closet, I've kept them all around for now. It helps a lot with space management if the retro PCs are in laptop format. For Win98SE era and later, this seems to work fine, I've been surprised how great T41 is for Win9x retrogaming, for early Direct3D games. Heck, I even got the Interstate'76 (both the GOG version, and my original CD version) to run 100% correctly on it, even the flamethrowers work now.
And yeah, I also have two retro consoles around, PS2 and the original XBox. I don't see much difference keeping them around, and my old PCs. I could certainly save some space near my TV if I got rid of those old consoles.
And as some have suggested, PC is pretty much the ultimate museum for running also old console games, starting from less known ancient gaming systems like Texas Instruments TI-99/4A etc. With consoles and most tablets/smartphones the emulation is a bit quirky and many times requires jailbreaking or modding your device. As long as I have PCs capable of emulation, I don't see much point trying to get e.g. my ASUS Android tablet to emulate the same.