Comment by the_why_of_y

Where did you get the idea that Haskell is a complex language? The core language is just 6 or 7 different expressions, everything else is syntactic sugar - it is in fact much simpler than C.

One of the reasons it's not widely adopted is that the features that programmers take for granted, like built-in syntax for mutable variables, are missing, i.e. it's too simple.