The Mac's entire brand identity can be summarized in three words: "It Just Works." Any time people see a machine running MacOS where those words are not true, it damages the entire brand.
Thus Apple is happy to forgo the extra revenue they could get by selling MacOS separately, since by doing so they can ensure that the world is not full of crappy beige boxes slapped together by incompetent OEMs sourcing parts from the lowest bidders with the word "Mac" attached to them.
Thus Apple is happy to forgo the extra revenue they could get by selling MacOS separately, since by doing so they can ensure that the world is not full of crappy beige boxes slapped together by incompetent OEMs sourcing parts from the lowest bidders with the word "Mac" attached to them.