The Desktop isn't prime real estate when you are actually using your computer and have windows covering it. Then it becomes cumbersome to access anything on it, even with a one click show desktop button.
Having the desktop not also be a file dump by default and instead a space for mostly useless widgets was one of the few good things KDE 4 did.
Key issue driving any conversation about desktop environments; so many people have vastly different workflows and expectations for their computer.
Personally, I keep my desktop absolutely sterile, usually some geometric patterned background, and that's it. Autohiding taskbar, no shortcuts, etc. It keeps me from having the "stepping into another room" effect when I sit down at my computer, which I'm very prone to. That means I can hit win/option/spotlight depending on the comp and launch the program I sat down to get into, without thinking "Oh yeah, I meant to edit that excel file..." and going on a 30 minute tangent.