One analogy for the 3D art that I've heard is to liken it to photography. If someone makes "art" photographs, say with a (human) model in a fancy dress and holding a sword, the photographer still owns the copyright to the resulting photograph, even though he didn't make the model's clothes or the sword (or the model!). Generally, unless the human model is well known, even her name remains unknown to anyone viewing the photograph. The photographer probably paid her a modeling fee and obtained a release form, which is analogous to the fee paid for a 3D model and the "readme" file that comes with it outlining its terms of use.

Some artists really embrace the 3D realm, considering it just another tool with which to express themselves. For the non-artist who is comfortable with the technology, it can really unleash creativity, since it removes the learning curve for other media like paint or pencil; it makes dealing with (and learning about) perspective on a 2D surface much easier, since you can move "real" objects around in real time; and it makes experimentation much easier. ("Don't like that pose? OK, how about I move this hand behind the back, and tighten the grip on the sceptre, and oh let's make it green instead of blue...") And all done with just a few mouse clicks.