How come, in the movie Cool World, when Holly Wood is on top of the artist and they're getting it on...?

The artists didn't draw her nipples... you should be able to see their shape through the nightie or whatever she is wearing. At first I thought it was cause that would be too revealing or something - but imediatley after she turns into a real human and you can totally see them! Why do they bother hiding them when they're animated, but let you see even more when she's real? Isn't that worse for ratings etc?