(retrocomputing.stackexchange.com)
Most likely it was a deliberate technical limitation. After all, dialog windows themselves were already overlapped. I remember well what a headache it was to program and render graphical elements on those old machines (PC AT 80286 with 256 KB of RAM).
While it's demonstrated to be likely incorrect here, it's not a wild theory. Apple and Microsoft spent a lot of time in court over the "Look and Feel" cases regarding the windowing UI Apple felt Microsoft had stolen. The lawsuit was first filed in '88 and was widely reported on in tech and mainstream press etc, dragging on throughout the 90s.
https://en.wikipedia.org/wiki/Apple_Computer,_Inc._v._Micros....
> The likelihood of any legal restriction was probably close to zero - it’s only from today’s era of hyper-regulation that we might even imagine something like that.
Normally I'd agree with a statement like this. Except this is a very specific case.
At the time I remember reading that was kind of the issue. I thought the article said something like "when Gates saw the Xerox machine, the display had no overlapping windows". So M/S cloned it as he saw it.
Once M/S W1.0 was developed he saw the demo again and was surprised the windows overlapped. So they rushed 2.0 to fix it.
But funny, with all people on Linux using tiling window managers these days, it seems Windows 1.0 was ahead of its time :)
And tiling still largely doesn't work with small windows.
(this was around IRQ13, IIRC,right?)
For me the revelation was that I have never said "Oh boy I sure am glad this window partially overlaps this other window" I either want one full screen windows or a few windows side by side. Why do I have to handle this myself? and went to the dark side, a tiling window manager. To the point that it really chafes now when I use stacking windows, It feels like I spend most of the time shuffling windows around.
To ease the overlapping window pain many linux window managers have a feature where the focused window does not have to be the top window and this makes things a lot better, you can be looking at the top window and typing/clicking on the partially obscured bottom window.