Microsoft started with a mission: to power the world’s hardware. Hardware was forecast as something of a commodity and the software became the value-add which brought forth the uniqueness of user experience onto lifeless devices. This viewpoint was convincing for two reasons. First, it made business sense for Microsoft to specialize in one core function in order to develop and maintain a competitive advantage. Second, building hardware requires the amalgamation of a handful of suppliers, making it difficult for any one manufacturer to gain a competitive edge.
Apple has always held a different understanding of the world: hardware is designed uniquely for the software, and vice versa. As soon as you generalize either to support multiple platforms, the end product and user experience will be compromised. This explains why Apple has never licensed its operating system to PC manufacturers and why Apple refuses to sell hardware running Windows software.