Different paradigms. macOS is app-document based while Windows is, well, window-based. Some functionality is also delegated to Exposé/Mission Control.

It all depends on what one’s used to. I always end up frustrated trying to daily drive window-paradigm desktops (including KDE, etc) because windows being the only logical unit of organization makes keeping everything wrangled feel a lot more difficult. As a result, I only run Windows and desktop Linux distros on machines that I’ve assigned to a single purpose (which only ever see 1-4 windows open at any given time).