It is not nostalgia alone, its also the fact that quite a few older games do not work on newer operating systems at all, or they do not work so well, also emulators tend to look considerably better when run on old video cards, without having to jump through hoops like on modern cards.
If you are into retro games and gaming, having retro hardware is more of a "need" than a "want", at least thats my opinion. Or maybe i could rephrase that as "if you want a good experience with retro games and emulators, you need a retro computer" :P
Oh and definitely CRT is a must. Still pictures look much better on modern displays, but on games...CRT blows any modern monitor out of the water, even on newer games.

There might be a few, but I haven't encountered them yet.

I wouldn't say "feel the need", but more "why not?". If you have the space anyway and 30 years of cast off PC components from upgrades...why not use them? I especially prefer using an old PC for DOS games with original sound card. Hook them up to one of the last great flat screen CRT's and they just play better, sound better and look better than emulating. It's not just the games though, it takes me back to a time when I still found the hardware side of things actually interesting.
Emulation may provide you with the game, but it doesn't give the entire experience of playing on PC in the 90's or earlier and that's what I'm after when I'm in the retro mood.

Even when going after that experience (YOUR experience from the 90s), it'll always be an "emulation". Only turning back the clock will give you the real thing. ;-)

Absolutely. With Mac OS X 10.15 Catalina, support for 32-bit apps was dropped, leaving a lot of even fairly recent Mac games out in the cold. I still have MacBooks in my collection running 10.6.8 and 10.7.5 (plus several others for spare parts) because some of my games seem to have been broken on newer versions of WINE, or are PPC-games that require Rosetta. Compatibility with some source ports is also an unknown too with the big Apple Silicon/Big Sur transition.

Plus there's just the nostalgic and aesthetic joy I get from gaming on old hardware too, especially old machines that I've upgraded and stretched to its limits -- be they legacy PC or Mac hardware.

I do have a retro computer, it's an Atari 800XL with two 5 1/4 drives.

A windows 95 machine, maybe

When i have the room again i'll will be reviving this old xeon though, give it a new casing, some new fans, keep it quiet as ever... might even try a closed waterloop.. premade but it might as well be revived as 1920x1080 platform and nothing else... Vista would have been the choice at first, but with all ' older ' games working mostly again like they should i just keep windows 10 installed...

probably the same will apply for the win95 device

for older era's i say no thank you very much

For MS-DOS games, no. I feel DOSBox runs MS-DOS era games pretty much perfectly, and I don't see any benefit running the same games on a real MS-DOS PC. It is actually better on DOSBox because you can easily change the DOSBox speed, as some games had some issues if the hardware was too fast or too slow (e.g. Shattered Steel).

For early Windows 9x and some XP games though, it may be hard to make some of them work on modern PCs. For instance I have the retail version of game Peter Jackson's King Kong: The Movie, and due to its copy protection it runs only on Windows XP (and possibly Windows 9x, not sure...). I am unsure if there is some crack that would take care of that problem.

It is a bit problematic game because it is late PS2-era game (2005) so it needs a pretty "beefy" retro-PC, so I originally couldn't really play it on my oldest Windows XP PCs as they were not fast enough for the game. However I recently installed Windows XP on one 10 years old laptop I acquired, and the game runs perfectly on it.

I rather play old games with emulators or compatibility fixes on modern PCs, for convenience. So I use old retro-PCs only if I have to. Heck, I am hoping that I don't have to power up my PS2 console anymore either, but play all the games on a PS2 emulator (I haven't powered up that PS2 for maybe 2 years, not sure if it works at all anymore).

Old PC games that I currently have installed on some older PCs because they tend to be quite problematic on e.g. modern Windows 10 PCs (not sure if someone has succeeded running these fine on Windows 10):

1. Mechwarrior 3: I've heard its physics break if the CPU is too fast, hence I am running it on one of my older Windows XP machines where it seems to run fine.

2. Blood Omen: Legacy of Kain: It is installed on that same XP machine, and even there it needs some fixes to run fine. The newest PC where I've gotten it run satisfactorily is my 8 years old Windows 7 laptop, but there it had the bug where the road signs are not displayed at all (this issue seems to be related to NVidia GPU incompatibility; on another laptop where I had Intel HD GPU, this bug didn't occur).

3. Peter Jackson's King Kong: The Movie which I mentioned earlier. Its copy protection does not work on Windows 7 or newer. Not sure if it would if there was a working crack for it (I think I tried to locate some noCD crack for it earlier...).

4, Nocturne. Not sure if this can nowadays run fine on modern PCs, but at least it runs fine on my old Windows XP machine.

In addition to those I am sure many of my older retail CD games will not work on Windows 10 due to SecuROM or SafeDisc copy protection, but these can still be made work on Windows 7...

same , those just take up space and if something cant run with emus then i just dont play them , there are so many games out there missing some is fine

I think the closest I got to doing something like this was buying a CRT and a PS2 so I could play Silent Hill 2/3, but that was only because SH2/3 have really poor PC ports and at the time PS2 emulators couldn't play them properly. But neither of those games really count as retro.

Living in a small apartment I can barely find space for my PC and TV and consoles plus my games, books and movies. I don't want to throw more stuff in there. Emulators and GOG takes care of most of the retro gaming cravings plus we get so many new great games that I want to play that in case an old game doesn't work anymore - well, I have a hundred other games that DO work that I can play instead.

I highly recommend looking into old thin server clients. They're tiny and they are great for retro gaming if you get the right units.

I have a couple but the main one I use for Windows 98 is a t5720 with an ssd (pata to sata connector). I also have an old htpc acer revo r3610 for Windows xp which I overclocked and put a better fan in and another client I use for msdos (forget which). They are all tiny (smaller than A4 paper) and take up next to no space. The t5720 is fanless and I have an external graphics card (geforce 5200) that is also passively cooled but as the expansion case is so rare it runs outside the case.

Cheap too as the 2 thin clients cost me under £40 each. (The acer I bought new when it first came out.)

It may not be as perfect as designing my own from scratch but apace wise they can't be beaten.

https://www.philscomputerlab.com/hp-t5720.html

Not really no. I prefer to save space and keep it on my main rig.

I used to have a Windows XP system for some games to get real hardware accelerated EAX sound that just sounded better (if you have still have a soundcard supporting it). But since many years now, I haven't had space for an extra PC nor even a need to dual/triple-boot to Win XP.

Linux/Wine does an amazing job at 'emulating' older OSes, to the point where wine staging gives you EAX sound if your soundcard can provide it. So I just run Gothic 3 in win xp mode with EAX ticked on and it works with sublime sound. Happy gamer. You can even get EAX on win7, so that you get the combination of dx11 + EAX for a community patched Gothic 3. This is not possible at all on Windows, as there is no way to get EAX post-xp.

The rest of the actually older games I want, dos games like STar Trek a Final Unity, dosbox does an outstanding job. There's a new fork now I think called dosbox pure as part of RetroArch, which is now even more effective and simpler to use.