It was meant to be humorous, and from the perspective of a professional artist. They draw as a form of work, rather than entertainment, yet they recognize that the drawings that come out are fun, while simultaneously explaining that the drawings that hit the recycle bin (which should never go there in the first place, as a point of reference, instead of frustration) are typically what the fans don't see.
How many of Leon's pics do we see? What about Kitty's? Chances are they both get frustrated with how things don't turn out exactly they way they want them to until they manipulate the pictures a little, though either one has had reason to throw away something or have never had any fun with drawing.
It's really more of a perspective thing.