Because it was designed by autistic GNU programmers to have anything to edit shit under GNU/Linux. GIMP has an abysmally bad UI/UX and it has never solved it nor will it ever solve it, NOR will it ever replace Photoshop. It is a good program for technical edits, but it will never ever replace anything. It will remain it's own thing forever.
You can find
3.1 icons and menus in some of the deeper recesses of Windows 11.
https://youtube.com/watch?v=2GBs1GapIvw:684
Microsoft uses the excuse of "backwards compatibility" but that sounds like complete bullshit. A lot of these leftovers have nothing to do with backwards compatibility and are instead either visual or straight up superfluous stuff. Most people who need such old tools tend to be just using old PCs not connected to the internet instead of modern PCs.
And even if they are for some reason using some ancient software written in 1997 on Windows 11 there is no excuse such a big company which has a
de facto infinity money glitch going from the amount of users and customers they have to not updated and at least made it so the entire OS has a single consistent look and feel to it.
Please, fuck off. I don't want MS to suddenly rip all of the legacy menus out and replace them with WinUI 3 bullshit just because some faggot thinks that "old = bad" and "new = good" so change needs to happen because change for the sake of change is good. Nvidia is going to kill off their good old control panel in the name of a massive bloated app and I hate it. Microsoft killing off all of the legacy panels to do so? Fuck no.
And you wanna know the reason why there's so much old leftovers in Windows 11? It's because Windows 11 is essentially the newest version of Windows NT 3.1. Back in the 90's Microsoft was working on ditching MS-DOS+Windows in the name of a brand new OS which was Windows NT. They worked on it for many years, with the release of Windows 2000 and Windows Me being the push that led to them killing off MS-DOS+Win9x, and Windows XP was the first Windows based on NT both in consumer and enterprise space.
Now, here's an analogy. Windows, from Windows 1 to Windows Me, was in a way what GNU/Linux is. A GUI OS slapped on top of a CLI OS. This led to massive issues that culminated in Me being a flop and Microsoft moving to Windows NT, which was designed as a GUI OS from the ground up, with it essentially being an OS/2 fork. So your GUI in Windows isn't modular like it is in Linux, it is hardcoded and connected to the OS in such a way that you can't magically remove all those leftovers because you no like old thing.
@Gargamel is right. There is nothing wrong with those leftovers. They work, and you don't fix what's not broken. You know, like Wayland, which will be a thorn in the side of Linux users when it's gonna get forced by more and more projects because someone thought that X11 was bad because it was old. But it worked, and that's what all those Windows leftovers are. Old code that works and doesn't need to be changed.