For some reason when I take a long drawing hiatus, I seem to improve dramatically. Practice and constant drawing often seems to actually hinder my progress as my brain gets clogged and stagnate. I take a long break, and come back with a fresh set of eyes and brain, and that usually gives me a huge boost to the way I draw.
Such pattern leads me to assume that drawing skill is innate in everyone, and all that is required of people is a proper way of thinking.
I have an old example I usually bring up when talking to people about art. The rabbit problem.
You take 2 drawings. One poorly drawn, and the other one, traced from a photo. It will take no more than 1 second for someone to say which is a more realistic rabbit drawing. Your brain already knows what a rabbit looks like, how its muscular structures are, and what constitutes a good rabbit texture.
Recreating a realistic rabbit from your brain should only be a matter of time, not of skill. Your brain already possesses all the information that is ever needed. Sure, it may take some practice, but eventually you'll get there.
That is primarily the reason why I never use references, or use textures/brushes made by someone else. I already have all the reference I need in my brain. It'll take time, but I'll get there.