Agreed. If it weren't for a good life drawing professor I wouldn't have any idea about the "where" or "why" of lights and I'd hobble myself using front lighting every single time.
Anyone who is just putting a photograph in a hidden layer to copy from is inherently limiting themselves closely to the neighborhood of what is there and what can be photographed. How could you cross into hard core surrealism that way?
The drawing will be more of the same.
Photo refs can be very useful for things like understanding what kind of things might be attached to the outside of a combat vehicle or whether Chrysanthemum leaves come out of the stem in alternating fashion. Photo refs lead to a dull drawing, though, if they are being used to avoid dealing with perspective. Those camera lenses are just not as good as the human eye.