Why Would You Write A Book? It's a lot of time and a lot of work. What's the point?
You have important things to say to other professionals in your field—things you've worked hard to learn, that can be useful to others. You can help people.
Your book will enhance your professional standing—in your community, and among your peers. You'll display it proudly in your place of business. Imagine your clients' reaction to your book—with your name on the cover. You may receive new opportunities to speak professionally. Your book may even help you find and hire better people for your own professional team.
You'll be financially rewarded. Of course your principal source of income is probably your business, and so it will remain. But receiving a royalty check in the mail twice a year can't hurt.
It's part of your legacy. You've learned things that some unknown photographer a decade or two from now will need to know—and that future photographer will invent something altogether new, based on what she learns from you.