Is there some reason haskell binaries have to be statically linked? I can't seem to find a way to make them otherwise, at least with ghc.
The ELF dynamic linking format seems to be designed on the assumption of poor code reuse (e.g., C code) where calls from one module to another are rare and can therefore be expensive.
Haskell code has very high levels of reuse and calls from one module to another (especially calls into Prelude, List, Monad, etc) are very common so dynamic linking imposes a very high overhead.
This isn't a reason to not support dynamic linking but it's a reason to make it a low priority. Incidentally, it avoids confusion between the performance overhead of lazy evaluation and the performance overhead of dynamic linking of modular code.
Yes, and there are various other reasons too. There's a FAQ question in GHC's (rather well hidden) FAQ: http://www.haskell.org/ghc/docs/latest/html/users_guide/faq.html and a search through the glasgow-haskell-users archives will turn up previous discussions. Also, we do (or did) have support for dynamic libraries on Windows. Cheers, Simon