In short, it doesn't. It has value, but it doesn't need funding aside from the cost putting together the document. We aren't taking anything out as a result, and we aren't removing any stretch goals. It's certainly an incentive, but it's a free bonus to the community, not taking anything out. You'll see more stretch goals before and after GUMSHOE license if we hit previous ones.
Think of it as giving all backers a free puppy rather than breeding a new kind of super-dog.