@Avec: I think oil visually adds dimension, accentuates form, etc. May have psychological associations too associated with sexy times. Plain skin appears flatter, unless you got good lighting. The second photo appears to be an example of un-oiled skin.
Wasn't too appealing for me either with the oil, I like either 'matte' skin or skin with water on it. I think water droplets and rivulets look much sexier than some oil sheen all over