creating good textures is a lot more involved than just matching photos to a seam guide in photoshop, which is what a lot of vendors do, making them more of a vendor and less of an artist. It takes a lot of time and patience focusing on every inch of the skin from head to toe. A decent full body texture can easily take a good month or two to get right, not counting the added work in the materials room, and most vendors won't spend that much time on it, because they know the most they can expect from it is about $8 bucks per sale, $10 if they're lucky. Profit has to justify time invested. 

The z-brush artist that did the morgan freeman texture wasn't worrying about how much money he was going to make off of it - he was more concerned about demonstrating his skills as an artist, to add a new piece to his portfolio, to land him the next gig, so that he doesn't have to resort to making v4 textures for $8 bucks a pop.

 

~Shane