[mikhailt]

It is not a silly question, it's just that no one outside of Apple and/or ImgTech knows.

The most logical reason would be that Apple has all it needs when it started building its own custom GPU many years ago and ImgTech has no patents it needs, which is entirely possible despite what ImgTech has said.

It is also entirely possible that Apple knows it has a few patents it is infringing and because on its last several years of experience, it would be cheaper to go through a lawsuit than to license. The reason? By going with the lawsuit, you're likely to get some of the patents invalided and royalties drop. It is possible it could go the other way, Apple paying more but it is extremely difficult to provide willful infringement when Apple can provide evidence of its own custom work that started before ImgTech was used in a clean room environment. But that's also easy to mitigate if ImgTech shows Apple hired the key personnel that worked on the same technology as the personnel should've known it was patented.