I think that if the only motivation for the novelist to write that exists is making money, there are about a zillion other ways they can do that more effectively than by writing books. I'm motivated to make sales, but mostly when I've been writing actively it's to fulfill a creative outlet, and part of an innate need I have to tell a story whether anyone reads it or not. It's hard work, but it's also enjoyable to me for the most part - I like creating characters and settings, coming up with backstories and doing research, then putting it all together in a cohesive way.
