I think it mostly derives from the fact that macOS has a far more cohesive concept of "application" than Windows does. A Mac app's files are managed as a group (the app bundle), execution is managed at the app level (traditionally, closing the last window did not quit the application), window visibility can be managed at the app level (show/hide as an alternative to minimizing). So cycling through apps is a very natural thing to include as well, and once that shortcut exists it makes a bit more sense to have a second shortcut to cycle within an app's windows than through all visible windows. Especially once Apple introduced Exposé/Mission Control, there really wasn't much need for a shortcut to cycle through the full list of windows, because there are plenty of other ways to select the window you want in fewer steps.