Why do some people never improve at art?

No.5874524 ViewReplyOriginalReport
How is it that people can draw for 10 years and barely or not improve at all? What sets those people apart from those that become fantastic artists within a few years of learning? I've seen art from people I knew back in high school and they still haven't improved since graduating.

What habits create a stagnate artist and what ones create thriving ones?