That's not quite true. If you delete an app from the app folder on a Mac, 99% of the time you'll get 100% of the binaries associated with the app. You'll leave behind inert configuration information in /Library and any relevant ~/Library folders, but that's all.

On Windows, binaries end up strewn all over the place, including C:\Windows, which is one reason that C:\Windows grows inexorably over time (even under 10) if you frequently install and uninstall software, and the only approved-by-MSFT approach to shrinking it is a wipe and reinstall.

Now, the Mac doesn't prevent installers from doing goofy stuff, or from dropping binaries more widely. VMWare, for example, does this, but VMWare is also doing something more elaborate than an Office app. Adobe does this, but that's Adobe being a jerk -- there's no technical reason they need to do it.

And anyway, you can easily go into the folders in /Library & etc to zap the leftover stuff if you want -- there's no Registry or anything that would cry foul. It's just that most people don't bother.