His point was to demonstrate how, by exercising hard, we can improve our sketching technique as well as our skills. Back in school my teachers used to say " to draw well you must exercise over and over untill you get sick of it"...they were right!
With this drawing Spencer Nugent shows us exactly the same thing, the blu line drawing is one of his first car drawings ever made and the black line one is a recent one done on an Ipad.
This is a fact, Spencer Nugent is a well known designer and internet professional reference in our field with the website IDSketching.
I think that one of his strong points in drawing is the good sense of perspective and his skill in managing the linework quality.
So what are you waiting for? Go back to your drawings :)
For a video tutorial click: car sketching video demo