The whole Paladium trusted boot/"known OS environment"/etc stuff could very easily have gone down the path of "This hardware only boots Windows." Secure Boot has been a pain for a while, though at least you can turn it off.

Nobody at the time (as far as OEMs) seemed to care the slightest bit about Linux, so the concern of "Only boots a measured Windows install, for your own security" seemed rather worth worrying about.