Well you're describing GNOME, and most desktop Linux distributions default to GNOME. So your question is really "why do they default to GNOME".
"most major desktop OSes" is an interesting phrase because there aren't that many. macOS obviously pioneered the "dock", and Windows eventually copied it, because that's what Microsoft does. The only other "major" desktop operating systems are the various distributions of Linux. BSD-based operating systems are in no way "major".
If you don't like the dock, you would probably like KDE Plasma.
"most major desktop OSes" is an interesting phrase because there aren't that many. macOS obviously pioneered the "dock", and Windows eventually copied it, because that's what Microsoft does. The only other "major" desktop operating systems are the various distributions of Linux. BSD-based operating systems are in no way "major".
If you don't like the dock, you would probably like KDE Plasma.