Imagine you are a beginner, you never worked on a paid commission. You open your "Finished Illustrations" folder, you look at your stuff and you say:
-Yeah, I'm ready to roll.
So you go ahead and make a portfolio. Then you start emailing every art director you ever heard about.
My point is: how do you know that you are good enough for it? It would be nice too if some of you could post your first paid work for a studio.