"Former Microsoft (NASDAQ: MSFT ) exec Craig Mundie, who now serves as special advisor to Steve Ballmer, recently explained why the company needed to launch Surface. It was taking some blame for low-quality devices made by hardware partners that weren't willing to invest in quality due to their already low margins."
Those low margins were due in part to Microsoft's habit of extracting every penny it could through the "Microsoft tax" without reducing the count of OEM's through bankruptcies. I.e. it had been charging "all the market would bear" for Windows. That is why the products of Windows OEM's had always been lower than that of Apple products.