@codewiz I don't think the issue is with firmware development support (which is horrible for all vendors) but on the hardware side: apparently it's much easier to do a small-scale laptop production run with Intel than it is with AMD.
With Intel you can get a reference design, maybe even some support through some inept intern to help you sort out your customizations before you've sold the first Intel chip. With AMD you won't even get a phone call with their sales rep if the expected $$$ is too low (or so I've heard).
Simple reason: Intel can afford to waste lots of time on customers that usually get nowhere if that also means that they'll invest in the potential biggest computer vendor of the following decade (who will be nudged to optimize their workflow to work with Intel, and Intel only).
@codewiz You need both. The coreboot side is covered now due to Chrome OS firmware supporting it (same as with Intel post-Sandy Bridge) - but if the first impulse of any device vendor is to go for Intel because it's easier to crank out devices with them, even "highly visible" stuff like coreboot (only highly visible in certain bubbles in my experience) doesn't help.