For me: Because it’s cool.

I play around a lot with retro networking and have exposed myself to all sorts of old protocols, technologies, etc. that maintain my interest much more than the IP monoculture of today.

Also I get to practice skills I otherwise wouldn’t. I’ve done more hardware hacking reverse engineering in retro stuff than modern stuff, partially because it’s simpler, partially because I actually have a real goal or objective, versus just doing something for rote.