But those need to be clicked with the mouse. Having a top 10 list of extremely common hotkeys in an app is just a lot more discoverable (for the non-expert or first-time user) and much faster (for all users) than finding the right icon to click.
You don't remember all the cardboard keyboard overlays that used to ship with software?
But also comes with a cost and complexity including users having to sometimes look onscreen for functions and sometimes on the keyboard.
Apple's done this with great success in their re-use of the f-keys as system control buttons (as have other manufacturers.) I'm not sure most Mac users are even aware those are f-keys any more.