Could be lawyers at some companies just didn't want anything to do with the GPL, especially if they're fiddling with the kernel itself. Maybe they're not even correct about the details of it, just fearful. "Lawyers overly cautious" is not an uncommon thing to see.
Having seen the screams from some people when you use GPL legally I can't blame the lawyers. You might be correct but you will still get annoying people yelling you are not. there is also the cost to verifying you are correct (we put the wrong address in for where to send you request for sorce, fortunately a tester caught it before release, but still expensive as the lawyers forced the full recall process meaning we had to send a tech to upgrade the testers instead of saying where to download the fix)
