That and tracing are very common.
What, did you think that all those great pictures were just "from the head?"
As an artfag, I've seen a lot of tricks that they use, from real life photographs to 3d models posing.
I don't blame them though, tracing is a legitimate technique with a purpose.
The reason why you see so much of it nowadays has mostly to do with the pressure to quickly release as many pictures as possible every artist feels because the environment is so competitive and if you don't, then you will be quickly forgotten about.