To make sure we keep this on the question originally posed... Realism is sort of the Holy Grail of many 3D artists and craftsfolk. Dailyn is right that there's nothing "real" about a texture put on a model with a vacuous look, but at the same time, compare those to the renders done by folk like Catharina, where you're really pushed to tell the difference between them and a photo, particularly her black and white work. I think part of it just comes from the sheer challenge. I've created Bryce renders that folks have looked at and swore were photos, and I gotta admit, that gives me a real charge. I haven't gotten that close in Poser yet, but it doesn't stop me from trying. And I know that it's more than just a texture with moles and freckles, although those are great starting points. There are other things to remember: like making sure the model is actually looking at a set point in space, that the facial features aren't exactly symmetrical, that an expression is a combination of dials, not just plugging 1.0 into the "worry brow R" dial and walking away.