Closing an app

Mac apps routinely have more than one window visible; quit and close are separate.

Apps with one window open will usually quit when you press the red 🔴 close.

Other apps will require a specific quit request.

macOS does a pretty good job of managing apps foreground and background too, so opening and closing isn’t something users need to focus on, much as Apple has been working to remove the Save control in various contexts. The intent seemingly being that the user doesn’t have to know to do “the right thing” here for saving or for quitting; that macOS will manage this for the user.

But for other cases, ⌘Q, as you are well aware.

Or more succinctly, macOS is not Windows.

As for why Apple doesn’t add a forth (quit) button to close all, nobody here knows. Log your fourth-button request with Apple, as they may or may not see it here: Product Feedback - Apple. pending that, use ⌘Q. Or ignore it, and let macOS manage the apps.

What’s the point of quitting an app? All memory will be relinquished when you stop using the app. OCD is the only concern I can see, but that’s easily remedied by quitting the app.