It's a mixture of things....
First off, there is indeed nostalgia. I was born in 83', I grew up through the growth of the internet as we know it, and I participated in it big time once I had a computer of my own. I was a kid in a single income home - we called it upper-middle-class with lower-middle-class income - with a small sect of richer quasi-relatives who DID have PC's. I had so many crazy experiences. Sneaking into the Auburn Draughton library to surf the web for free during the rise of the internet, cutting my teeth on DOS on my sister's 386 trying to play Freddy Pharkas - which I was FORBIDDEN to play (and getting in trouble). Due to the income of my household, I was always behind one or two generations technology wise at least.
And I get nostalgia twice because I started doing all this 20 years ago, when I finally COULD afford a 486 because nobody wanted them and I could get them for free from family/friends all day long. That's when the whole "Creeping Network/Creepingnet" thing started. Just as much as I miss how magical things were in the early 90's, I also miss how things were in the early 2000's when I Could back my truck up to the local Salvation Army and come home with 20 old x86 PC's and a pile of DOS big box games for a song. I regret selling/etltting go of a lot of that stuff. I've tried many times over the years to move to Emulation and give up on old hardware, but I miss the tinkering. The hardware is just simple enough you can tinker with it like I tinker with the electronics in my guitars that eventually lead to me BUILDIGN my own guitars. I'm now starting to look at making my own PC hardware for old platforms.
But unlike my other retro-platforms, such as consoles, or old rock music - it's not as dead. If anything, I think the x86 PC has been on the rise since 2010. It's crazy, I started a YouTube channel for PC's that ended up a guitar channel from 2006-2010 mostly because nobody cared about 386's or 486's back then - then suddenly 2010 comes, I-pad guy becomes 8-bit guy, LGR takes off.....and I regretted getting rid of all that old hardware because I was very much missing playing these games on the real thing, and find a lot of modern solutions to be too fiddly, especially back then.
A fine example of fiddly is RetroPie - I got one of those two years ago, I spend more time updating/fixing/tuning/tweaking that d*** thing than I do my old NEC Versa M/75 which I just flip the switch, kick off whatever I intend to do, and it just works as intended, maybe even better with the improvements I find from places like this forum and elsewhere or figure out myself through experimentation.
I'm also a HUGE research nerd, and one of the most fun things for me is hunting for underdogs. That's why I jumped down a super-deep NEC Versa rabbithole recently, and why I have done so with NanTan's laptops, weird old whitebox makers like GEM computer Products/C.More/MEC, or AMT. There's so much weird oddware and crazy stories, and neat undiscovered models of PC out there that few people talk about let alone know about and the fact that there were millions of these things made in their day means I'll never be bored till the day I die.
And then there's an aesthetic to it as well. I'm a huge Vaporwave/Retrowave fan, and a huge 80's music fan as well. Something just feels right cranking some Timecop83 or Top Gun while playing Monkey Island and sipping on a cappuchino. Or slaying monsters in Diablo with Iron Maiden in the background clad in denim. Plus I'd enjoy the crazy looks I'd get ) if I turn up at a local starbucks surfing in LInks on an early 90's laptop tethered to my cell phone - esp if I happen to be wearing a beanie and flannel that day.....like some kind of grunge rock time traveler. It's so much more interesting and socially acceptable to use old hardware these days than it was when I HAD to use it because that's all I Could afford, so I can sometimes have fun and even good nature make fun of it. Also, I just love the look and style of 1980's and 1990's computer design - right angles, lots of vents, digital readouts, lots of gray, beige, with blue, red, aqua - accents. To me the old stuff looks more "high tech" than the stuff today that looks like someone's strange art-piece, or a tea tray from the "Le Flats D' Colletion NYC - est. 2020" collection.