Nobody's going to reimplement an entire graphics stack in Haskell (or any other language, except as a tour-de-force with no practical use); they're going to use existing bindings to a well-tested existing GUI.  Rewriting Wx or Gtk+ in Haskell, seriously?  Aside from the effort required at the outset, try keeping up with changes to the thing you're reimplementing.  Not maintainable and not viable.