I write math texts that are Free. It is my creative outlet. My Linear Algebra (http://joshua.smcvt.edu/linearalgebra) has gotten some traction (and I get a small amount of money from Amazon). I also have an Introduction to Proofs: an Inquiry-Based Approach (http://joshua.smcvt.edu/proofs) that I find helps my students, but is in quite a niche area. And I'm working on a Theory of Computation.
If I didn't have some creative work I would be much less happy.