Pushing off the breakage to the hypothetical future is how you end up with the Win32 API---Microsoft actually had to go and reverse-engineer their own (C++-impl

Pushing off the breakage to the hypothetical future is how you end up with the Win32 API---Microsoft actually had to go and reverse-engineer their own (C++-implemented) classes into C structs because apps like Photoshop were digging through private structures to squeak a bit of performance out of the system that the APIs didn't directly allow for. When changes in the C++ implicit rules changed the layout of the structures the compiler made, big-name apps would break and Microsoft got into a state where they couldn't release a new OS without "breaking Photoshop." Apple would rather not be shackled to popular developers cracking open their design to do things that are forwards-incompatible.