For the main line cruise companies, I think it is more about logistics as much as anything. Air transport, moving several thousand people from the airport to the ship, luggage, re-provisioning, etc. But I imagine air alone make it difficult at best and then the other items just do not make it work well to port a big ship out of SXM.
When you think about the logistics just for the cruise ships in MIA and FLL, it is an extremely complicatetd operation. Not that it could not be done, just that why would they want to do it and what is the benefit to them, remember their idea is to make money! <img src="http://65.246.19.145/forums/images/graemlins/Grin.gif" alt="" />