When I was young, I started my journey into the computing world on an Emachines eTower 366i2. It ran #Windows98. There were also #Windows95 computers and a single ancient (even at the time) #Windows3.x computer around me, but our computer was running Windows 98. By Windows 98, almost 100% of the Windows interface was already set in stone (until Windows 7 that is, but we will get there). We transitioned to XP at some point, using the product key you all remember.
I think my XP VM might actually have that product key now.
At that time, #Linux was immature for the normal user, and #Mac was still overpriced (compared to their arguably fairly priced position now). Windows gave you a mature platform, with only enough connection to home to make your life easier (namely #WindowsUpdate), and a system that promised and delivered more reliable performance than previous generations. Not to say it didn't blue screen, but it tried to gracefully solve it's issues.
And it stayed this way for a bit. Through #Vista, and #Windows7, the general interface was the same, even though some backend things changed (Documents and Settings -> Users for example; but even that is still linked on Windows 11). The mature start menu was better than anything competitors could provide. It was more intuitive than any of the major Linux desktop environments and than #MacOSX.
But now, we get to the point where things began to change, and people began to violently hold onto their operating systems. Enter #Windows8. As far as I'm aware, Windows 8 was only or at least mostly distributed as an upgrade disk, as opposed to the previously majority clean install disks and keys.
As far as I'm aware, the last time Microsoft did this was for #Windows98SE (arguably just 98 with a service pack, because Windows Update wasn't as mature back then, and many households didn't even have an internet connection). So your options were to buy a new computer or abandon your earlier Windows install. Understandably, this pissed some people off. In 2013, I began to transition to Linux (Ubuntu at the time), and my household attempted to transition to Windows 8.
Unfortunately, Windows 8 was so resource inefficient that it made our former devices almost useless. #Windows8.1 improved performance and reliability a little bit, but it was still kind of a joke. Beyond that, Windows 8 no longer offered you the mature, intuitive interface Windows was known for. Instead, it gave you the Start...Screen(?)
It was weird, and thankfully my household moved to Windows 10 as soon as possible in 2015. This is arguably the first Windows version that was released almost exclusively online. It also is the final nail in the coffin for those who were concerned about privacy. #Windows10 and #Windows11 phone home constantly, don't really provide the mature interface everyone wanted, and Microsoft had already hemorrhaged users due to Windows 8 and to a lesser extent Vista and 7.
There are still people holding onto #XP and 7 to an extent that seems odd from those of us who updated as Microsoft wanted us to, but they are easily divided into a few categories that match up with the benefits Microsoft's Windows no longer provides:
1 Interface - An XP user, even a poweruser, probably would be confused or frustrated with Windows 8 or later. The interface is so far gone from the computer they used 15 years ago that it no longer looks or feels like Windows.
2 Privacy - Anyone who used *nix, or pre-8 Windows would not be content with modern Windows and the amount of places it sends random data to on a daily basis, as well as the Windows Update system.
3 Reliability - I'm not going to say Windows used to be reliable, but it used to mature with each update, not break further.
These were things that people chose Windows over all it's competitors for back then, but have no reason to anymore. So the attachment to XP or 7 isn't a nostalgia as I see it. Instead, it seems to be a very valid want of an actually decent operating system, alongside an unwillingness to switch to Linux.
Take it with a grain of salt though, because I started transitioning away from Windows in the XP/7 going into 8 days, and have been fully daily driving Linux for a solid 6-7 years now.