The prehistory is that developers for the Apple ][ had access to third party documentation, and made extensive use of unofficial system variables and entry points. The result was that it became impossible for Apple to update their own system without breaking popular apps and getting blamed for doing so. It turned Apple ][ technology into a dead end.

The Mac was intended to be a much more tightly controlled developer environment. And it came out at a time when there was still a lot of debate over the right way to develop a computing platform.

IBM had a different approach, which was to make things more open like the Apple ][, and they paid the price for it. For instance, a lot of the weird limitations of the IBM PC were caused by developers bit-banging hardware registers and video memory rather than going through "official" BIOS calls that were less efficient.

I don't personally know the right answer, but this is just the history as I recall it. At the time I preferred the IBM approach, because I could do some friendly bit banging and get stuff done, but my programs were mostly for a severely limited audience and lifespan. Today I try to do things in a way that insulates me from knowing anything about the platform that I'm using.