Well, this is easy answered. There are many vector apps on the market already (on the Mac side they all are cocoa/quartz based) who can not support CMYK color mode. Some promising projects mainly on Linux have the same problem. Inkscape and Skencil are still RGB based, sK1 is a fork of Skencil which will make it prepress ready including CMYK but all are far from the user experience you know from FreeHand.
We have asked some developers of existing apps if they would make it more FreeHand'ish, and nevertheless they are interested in such input, they can only go small steps into our direction.
Expressive is the only project which has specifically a FreeHand experience as goal and aims for this from the very beginning.