Most of them are from engineering fields, not from computer science. Their interest is designing and implementing engineering models rather than programming itself. So they are not as adventurous as computer science guys in investing new programming tools (languages).
Also, I am pretty sure more than 90% of them have never learned functional programming or related computational theories, even in schools.
You're answering to a guy who's been in 2 computer science labs focused on robotics! It is true that a lot of people have an EE/ME background, but I think you'd be surprised at the amount of CS people in robotics. Especially in SLAM which I mentioned, given that this is a probabilistic inference problem.
Also, I am pretty sure more than 90% of them have never learned functional programming or related computational theories, even in schools.