The reason why neither Samsung or LG are supported is that these manufacturers have chosen to go it alone and use their own proprietary and incompatible syncing protocols, unlike Sony Ericsson, Nokia, Motorola, Panasonic, Siemens etc. who all, sensibly, use the industry standard SyncML protocol.
Also, not only have they decided to shun the industry standards, they've also decided to shun Mac users by not providing Mac sync software, like they do for Windows users.