The idea of PC's slowing down overtime generally stems from user error more so than anything else in my experience. See with a console, the only thing you can really do is play games. They are purpose built. Sure you can do some other things like browse the web or play/stream media but at the crucks of it, it's main purpose is to play games.
A PC's main purpose is to do whatever you want and the user generally wants to do more things than just play games on a PC. Maybe they like memes and they want to make their own by installing photoshop. Well now you have Adobe's background junk consistently running. Maybe they are interested in Virtual Machines, well now you have to install programs like VMware or Hyper-V which have services running the background. Maybe they want to get into coding and such, well now you have to install additional software. Maybe they are super horny and wants to download TB's worth of prawn from shady sites that installed iamavirus.exe and the list goes on.
And this gets really yikes worthy if the PC has a mechanical hard drive instead of SSD. A console needs to run like maybe a couple of applications at once. But a PC? A fuck ton which again, as you load more software services onto the PC, that spinning disk gets more and more strain put onto it. It's one of the reasons why the move to SSD was a god send in PC use.
And don't get me started with pre-built PCs. You buy a computer from Dell and you don't do a fresh reinstall of Windows? You get to deal with Norton or McAfee anti viruses which drastically slow down PCs even with really fast SSDs. Not to mention all the shatware that comes pre-installed such as Support Assist and other nonsense. Oh and don't forget about all the dust that the more casual users don't clean.
Of course, I could go on but to quote uncle Ben: "With Great Power comes Great responsibility." If reinstalling Windows fixes slowdowns in your PC, that's not a problem with the platform, that's a problem with you and the shit you did to your PC.
PC Specs: CPU: 7800X3D || GPU: Strix 4090 || RAM: 32GB DDR5 6000 || Main SSD: WD 2TB SN850