Can anyone think of a reason why to do this? Apart from personal fun project, of course!
Because we hit peak desktop right around Windows 2000. Just about everything since then has been a step backwards in speed and usability. The Mac Finder is a hot mess and seems to get worse with every release. The 964 different desktops available for Linux are in general a hodgepodge of slow impossible-to-use disasters. A notable exception is XFCE but it's a bit of a second-class citizen and even things in XFCE don't…
I haven't been using Linux (or Windows) much since several years now. But a stripped down version of Gnome or KDE or MATE are prefect as they were. The Windows UI in its current form or old (95, 98 or 2000) is hardly the best UI choice. The reason I can think of is nostalgic fun experiment. And there is nothing wrong with that. Not everything has to have a practical function. :)