It forces you to learn a new and different way of thinking about programming and solving software problems. Even if you never end up actually using a functional

It forces you to learn a new and different way of thinking about programming and solving software problems. Even if you never end up actually using a functional language, many of the techniques and approaches you learn can be applied in all languages. Learning Haskell was probably the single best thing I've done with regards to becoming a better programmer even I've never really written much Haskell since then