Not require. But without a requirement, vendors are making their own choices. Some have gone with one-time programmable fuses to store the keys. Once programmed, only images signed with that key can be used. Otherwise, the device is a brick. Those vendors deserve to burn in hell (in my opinion as an embedded engineer that has implemented secure boot on a variety of platforms).
MS has been slowly prepping Windows on ARM to be viable as "Enterprise" device and for that it needs owner-controlled Platform Keys (to comply with their own requirements for enterprise offerings)
If you don't mind me asking, how did you get into embedded development? I'm trying to sample various types of development and see what I enjoy, and embedded development seems quite interesting to me though I've never done more than an arduino.
