Scalaz: Why use Scala if you're just going to make it as much like Haskell as possible?

Scalaz is a library that provides mathematical abstractions like Functors, Monads, and Monoids for Scala. Pardon my coarse comparison, but that sounds like "Haskell Stuff" to me. So why are so many really smart people I follow on Twitter using Scala with Scalaz and "Type Classes" instead of just using Haskell which has all that stuff already?