Because that's the market you can win when you're locked out of the mass market. But it's also not sustainable because then the mass market product will move up (Xeons based on x86) and you still can't move down with Microsoft blocking you.

Whereas if not for that, you could do both. Design a solid chip and then put dozens of them in a big iron cabinet for big money but also offer desktops with just one of them for prices that compete with Dell. Except that Dell's customers expect to open their existing Office documents and run their Windows API proprietary software and then won't buy from you.