The big wins from Haskell are immutability, pure functions by default, and expression-orientation... not the type-system, in my view. As to why it's not more p

The big wins from Haskell are immutability, pure functions by default, and expression-orientation... not the type-system, in my view. As to why it's not more popular? Well the entire industry caught OOP fever during Java's heyday, so platform holders pushed languages that were similar - see JavaScript, C#, Visual C++, etc... Now this paradigm has huge inertia, and smart software engineers are able to make it work (just about) anyway. In other words, an accident of history got us caught in a local minimum. Things are shifting though. The most popular framework in the world in probably React, and it's a (pretty crummy) implementation of functional programming concepts. It's not hard to find OOP thought-leaders advocating for immutability, effect systems and so on. Implementation inheritance is going the way of the singleton. I agree that Haskell in particular suffers from being lazy, which has genuine problems in practice.