Backwards compatibility with the ecosystem, especially the enormous ecosystem of software that doesn't have active maintainers chomping at the bit to test/patch/update with every single OS change, is a HUGE part of why people use Windows.
Apple really doesn't have this. Instead, they have a critical mass of software that is inside their RDF and actively updates to every breaking change they roll out. They have the "luxury" of not having to care if they break random bits of old software* in the process.
(* software that may be niche, may not have large individual user bases, but which might actually not have modern up-to-date drop-in replacements)