That approach won't work for anyone who uses their PCs in a closed-system setting. Software developers (such as myself), for example.
There are also a lot of PCs that live behind various firewalls or on private networks (banking, defense, security applications) that cannot, for legal or security reasons, be connected to the cloud just to be able to boot and function.
MS would be signing its death warrant in the enterprise world if they ever did this.

