I, in general, too, it seems that order - an incentive. And lazy people it may even proaktivirovat. Not even lazy, but afraid to start a new job. "Fear of a blank slate."
I'll usually write a book about two years (where I write something quickly, going for a long time), and given an advance for two books - both written for the year - not to give the same money back
True, there is another side to advance. Business (not in the works) I know that people are not very willing to work when the money already received. And here - wait for hack-work.