Retro Consoles are only sought out for because they're the only way to play certain old games legitimately
Pc games can easily be emulated/ported compared to some n64 game unless you're willing to pirate.
Thats not the Only way, trust me.
Also Emulation isn't illegitimate, its downloading Roms that is illegal. Ripping Roms is legal.
and even if by your logic that Emulators were illegal/illegitmate, would that mean that Nintendo Eshop classic games are wrong?
People play games on old consoles instead of newer ones or PC's because you can never Perfectly emulate the original hardware.
This reason applies to old PCs as well. Emulating a sound card will never be the same as having the real thing, emulation Dos will never be the same thing as running it etc.
It has to do with using the correct technologies.
TL;DR
The Same reason some people are reluctant to plop a PS1 Game into a PS2 or PS3 is the same reason people are reluctant to play Quake on a Modern Gaming PC.