Why is it so cool?
We have papers, many different kind of drawing and painting tools, and good models for free.
I like when the model doesn't try to do "amazing poses" but imagine him/herself in real situations and acts them out… Then I'll have a very strong impression of the pose, filled up with a character. (Unfortunately that isn't always like this.)
I love the strong simplicity of Picasso's and Henri Matisse's drawings. Their works influence me a lot when I'm drawing.