I find it easier to teach drawing to beginners than to teach it to people who think they know how to draw and have to unlearn what they think they know. Drawing is all about how you see the world. You have to look in terms of dark and light colored shapes, not objects in 3D space (which is how you saw the world before 10 weeks of age). 

A lot of people know how to fake it, but they don’t draw whats actually in front of them. To get them to start from square one again is not easy. …Most of these people can only draw certain things, given something like a piece of wrinkled, balled up paper they can’t draw it.

The whole point of learning to draw, and why it is considered the basic essential to art, is to open your eyes to the world, to the shapes and colors in front of you (which are well beyond what we imagine), not to reproduce something exactly. If an artist cannot ‘see’ the only thing they can draw, paint, whatever, is what their brains already know how to do. The brain is pretty limited in this respect. (How many doodles have you done in your life? Did you ever notice you do the same few doodle over and over? Thats essentially the extent of the brains’ creativity.)