I think programmers tend to underestimate the difficulties involved with becoming a good programmer because once you're good, you only see the even steeper learning curve ahead of you. Some of the smartest people I know work in other domains: biology, chemistry, and even physics. They are sometimes baffled by tasks that seem trivial to me, and I'm under no impression that I'm more intelligent than them. I simply spec…
On the other hand, if you think the software industry has a hard time figuring out (at hiring time) who the high performers are... science is driven by serendipity. Nobody can predict who will find the billion dollar discovery. Not even past performance is a reliable indicator.
So it makes sense to me that the salary spread in science is relatively even. If they could reliably figure out who to dump money on, they would. On the other hand, the FAANG companies clearly believe their hiring practices can select out the high performers... and perhaps they are right? If they're paying 3-4X what everyone else does, they expect to get at least 3-4X the value.