Corps don't want to have to release the source code for their internal forks. They could also potentially be sued for everything they link using it because the linked binaries could be "derivative works" according to a judge who doesn't know anything.
I'm wondering if you've ever actually asked a real corporate lawyer for an opinion on anything relating to GPL licenses. The results are pretty consistent. I've made the trip on three occasions, and the response each time was: "this was not drafted by a lawyer, it's virtually ininterpretable, and it is wildly unpredictable what the consequences of using this software are."
