Keyword being "was". Unfortunately most PC (and Mac, to an even greater extent) buyers today probably barely know who makes the CPU in what they're buying.
Also the choice is, and always was, basically between Intel and AMD. That's literally two options a customer has. When both companies implement a management engine across their CPUs, you don't have any choice in the matter.
I've had a handful of computers with CPUs made by VIA, so there's at least a small third option.