Ah, O.K I think I get what you're saying. It's a combination of a couple things. The light and camera are angled facing front and center, which will make most subjects look flat especially ones with a matte surface like what we see here. The dark areas are appearing because of the lack of bouncing light which looks strange with a white background, check out Final Gathering.

To expand on Dave's comment, many fabrics will have some degree of highlighting around the contours, this is caused by tiny fibers catching light. You could use a technique like this and adjust the gradiant colors based on how subtle the "fuzz" needs to be(see velvet near the bottom of the page).