This is not true. Driver quality is a major differentiating factor between GPUs and absolutely influences purchasing decisions.
GPU makers don't want their competitors to be able to take parts of their drivers and benefit from them. They want to protect trade secrets. They want to avoid revealing how many of their competitors' patents they are violating. They don't own the rights to some third party code or trade secrets that are incorporated in their drivers. They want to avoid revealing future product plans.
Of course it's debatable whether closed source drivers actually help with all of the above reasons, or whether they are good reasons to begin with. But those are the reasons.
AMD Radeon has made multiple of their performance-enhancing projects of theirs open source only to have nVidia copy and implement their work without reciprocating the favor.
It's not mandatory, but it sure isn't polite, especially when projects like HairWorks are killing AMD because it's a driver handling issue more than a hardware one.
This is not true. Driver quality is a major differentiating factor between GPUs and absolutely influences purchasing decisions.
GPU makers don't want their competitors to be able to take parts of their drivers and benefit from them. They want to protect trade secrets. They want to avoid revealing how many of their competitors' patents they are violating. They don't own the rights to some third party code or trade secrets that are incorporated in their drivers. They want to avoid revealing future product plans.
Of course it's debatable whether closed source drivers actually help with all of the above reasons, or whether they are good reasons to begin with. But those are the reasons.