Pretty much it's because we can't encrypt/lock SCX files, so people suffer no difficulties if they wanna steal models from SLRR. Plus SCX format can be easily imported to Z-Modeler 1 - and that's what used by most of GTA modders (at least for Vice City mods and to convert them into Z-Modeler 2 for San Andreas.)
So com'on, give these VIP guys some space, they can model, so they have the rights to decide whether their mods are going public, or can be only shared with their best gaming buddies, not the entire community. I used to be pissed by this growing VIP trend, but recently I started to realize they also have their reasons to keep mods hidden.
