In aesthetics, the uncanny valley is a hypothesis that describes why we find cartoons like XKCD more compelling, despite being stick figures, than drawings that are more realistic, but not quite accurate. If a piece falls in the uncanny valley, it feels eerie and creepy. So, unless you're confident in your ability to render something with high enough fidelity that it won't raise eyebrows, you're better off exaggerating features to make it less realistic.
For virtual reality to go mainstream, it'll to need to cross the uncanny valley. But, because people haven't been able to do this reliably, companies have shied away. With better technology, artists will soon be able to decide which side of the uncanny valley most effectively communicates their message. Until then, they'll keep devising creative ways to help people not get hung up on the details.