Probably not, but... There are stable and portable libraries that implement functionality missing in Haskell. It could be nice to be able to list then in a cabal file (using, say, pkgconfig-depends) and know for sure that any system with Haskell Platform will have then available for use with FFI. An example would be sqlite3.
w/o haskell binding it's useless for most of HP users
I think we currently address this by including the C libraries with the Haskell bindings (e.g. zlib).
That, of course, would be the goal. Today, it's disappointing to write bindings, since Hackage won't build them properly (since the libraries are not installed on hackage. Of course, for simple packages like zlib or sqlite3 you have the alternative of including them with your code). If good C libraries were available in HP, bindings would flourish. Maurício