That's irrelevant. The only aspect that is relevant is that the C++ standard does not define nor assume a standard or even fixed ABI, thus each compiler vendor just goes with the flow.

In some rare cases where a compiler vendor also controls the platform and essentially holds a vertically integrated monopoly, they are in a better position to not break the ABI all that often. Everyone else doing stuff in C++, whether writing programs or libraries or compilers or putting together OS distributions, just faces the music.