Stating that there are some number of cases of GPL violations that haven't been enforced or are in the gray area is not a logical base for the argument that the idea of having to share the source code should be abandoned. In fact, history shows otherwise - that Linux has had more success (as measured by uptake globally) than any other non-GPL open source kernel ecosystem.
Similarly, just because there may be people who can find loopholes in certain well-intended laws and regulations is not a good reason to abandon their intents. Instead, the questions should be - can we keep these intents and fix the loopholes or make the enforcement more straightforward? I think Google could, but maybe it's not in their immediate interests, one of which may be closer to - how do I upgrade the kernel without recompiling that other stuff.