I'll also add that type-classes are the main feature in Haskell that Python/Ruby cannot easily encode.

There are many interesting features that Python/Ruby/Lisp-variants can encode, but Haskell does with static guarantees, whereas Python/Ruby use dynamism (e.g: general polymorphism, "duck typing", various strong type system features that Python/Ruby do not "need" because they don't attempt to give guarantees, etc).