Intel and nVidia/ATI came from very different situations though.
The fear of nVidia and ATI was always that their "tricks" would be adopted by the $other_party. Imagine your driver has 5 tricks to make the performance 5% better in total: this is a huge competitive advantage. Now the other company reads those tricks in your source and can (legally) adopt them for their own drivers (adopting a programming construct or some trick isn't a copyright violation).
While this fear isn't completely realistic because most of the time performance isn't really determined by these sort of factors, it's also not completely UNrealistic because it certainly could be, at least in some cases! In a world where everyone is closed source and you're locked in a bitter rivalry with performance differences often being fairly small, it just makes complete sense to keep stuff closed.
Contrast this with Intel which just made integrated graphics: for much of its history performance wasn't a huge concern, and there wasn't really much direct competition either. There was never any reason to not open things.
The fear of nVidia and ATI was always that their "tricks" would be adopted by the $other_party. Imagine your driver has 5 tricks to make the performance 5% better in total: this is a huge competitive advantage. Now the other company reads those tricks in your source and can (legally) adopt them for their own drivers (adopting a programming construct or some trick isn't a copyright violation).
While this fear isn't completely realistic because most of the time performance isn't really determined by these sort of factors, it's also not completely UNrealistic because it certainly could be, at least in some cases! In a world where everyone is closed source and you're locked in a bitter rivalry with performance differences often being fairly small, it just makes complete sense to keep stuff closed.
Contrast this with Intel which just made integrated graphics: for much of its history performance wasn't a huge concern, and there wasn't really much direct competition either. There was never any reason to not open things.