We are not all Neil Gaiman. We can't all just write in whatever genre we want, whenever we want, and hope our audiences will follow us there. Established writers can't often-and probably shouldn't-publish far outside of their area of expertise. It's a fast way to alienate your existing fan base.
But if you're a creative author who absolutely has to write a children's book or a young adult novel, or an inspirational how-to, crowdfunding allows you to experiment outside of your genre for a project you want to see out in the world.