Cannot speak for industry, so speaking from experience in academia when we were learning functional programming (FP).
The key difficulty there is the paradigm shift in thinking. For most people our thinking matches imperative programming. Ask a person to do something like run an analysis of an accounting book using paper, pen, and a calculator, and you'll see them keep some tallies which they keep updating as they go along. Even if there was a way to convert their work into a method which just involves repeatedly tapping out the numbers into a calculator in a formulaic way, almost every time it's going to be easier to reason about the logic in terms of stored state and progressive steps.
When you get hit with the paradigm of functional programming, which is beautiful when it works btw, you need to switch your thinking from pure logic to formulae driven logic. That's an unnatural shift and given how poorly early schooling helps shift our thinking to that mindset when we do maths, it's a hell of a leap.
Anecdotally we had a couple of pros at math - people who understood the fundamental beauty of math and proofs - and they took to FP like ducks in water. Even when we built a library management system in Haskell.
The key difficulty there is the paradigm shift in thinking. For most people our thinking matches imperative programming. Ask a person to do something like run an analysis of an accounting book using paper, pen, and a calculator, and you'll see them keep some tallies which they keep updating as they go along. Even if there was a way to convert their work into a method which just involves repeatedly tapping out the numbers into a calculator in a formulaic way, almost every time it's going to be easier to reason about the logic in terms of stored state and progressive steps.
When you get hit with the paradigm of functional programming, which is beautiful when it works btw, you need to switch your thinking from pure logic to formulae driven logic. That's an unnatural shift and given how poorly early schooling helps shift our thinking to that mindset when we do maths, it's a hell of a leap.
Anecdotally we had a couple of pros at math - people who understood the fundamental beauty of math and proofs - and they took to FP like ducks in water. Even when we built a library management system in Haskell.