That's because the scientists often don't understand the philosophical problems.
It could be that the problems aren't real. The physicists are using the theory as it was intended, as a scientific theory, and the philosophers are confusing themselves by asking invalid questions about it.
This all depends on what you mean by "understand". Some people think "understanding the brain" or "explaining consciousness" involves denying its existence. That sort of understanding won't be enough. I want understanding that involves actual understanding.
I just mean understand the workings of the brain in an empirical sense. If free will is something that is forever trapped inside an unknowable consciousness, unobservable to science, then it's not really free will at all. Free will can make its presence known by (at least sometimes) being acted upon. We can empirically tell whether or not a subject has libertarian free will. It will sometimes introduce an element of unpredictability into their behaviour which we can observe.
What is the survival benefit of subjective consciousness at all? Wouldn't it have been more economical to have zombies instead?
If zombies were possible, yes. But if consciousness necessarily accompanies the right kind of complex agent-like behaviour then we don't need to explain it separately. We can't say the same for libertarian free will because this actually implies changes in behaviour, and thus requires an evolutionary explanation.
[edit] correction: In order to actually take advantage of free will - to put it into action instead of leaving it blindly coupled to the ego (unfree will), which most certainly did evolve (because self-interest is the driving force behind evolution), we need the capacity for rational thought. That also had to evolve, although much more recently than the ego. All creatures have the capacity to act self-interestedly. Only rational beings are capable of wilfully transcending this evolved capacity to act self-interestedly, but rationality alone is not enough. We also need the self-discipline ("will-power") to make it happen. [/edit]
As Dawkins put it, in the infamous last sentence of the Selfish Gene "We, alone on earth, can rebel against the tyranny of our selfish replicators." But, as many people have pointed out, he never explained how that was possible, why evolution would work against itself in this way, how it could favour creatures that were unoptimised for their own survival in this way over more "selfish" creatures.
Besides, it seems to me that rationality, in itself, does not make us altruistic. If our biologically programmed instincts are selfish then we will act rationally in pursuit of them. Being rational doesn't provide us with new goals.
The fact that compatibilist free will might be deterministic does not mean that we need to apply the term to machines, unless it's just a synonym for computing. In an event, compatibilist free will also involves randomness, so it doesn't apply to computers (at least not yet).
