Successful people often have a lot going on in their lives. At the very least, hiring a coach helps bring focus to the project and if the coach is right for you, takes you places you might not go otherwise.
Think of a coach as someone who will be in your corner, dedicated to help you marshal your forces and move forward. You can always depend on them to be focused on you & your goals, unencumbered by outside influences or their own internal issues. One of the best things I ever did for myself was hire a writing coach to work with me on my new book. Yes, I could have done it on my own, but having her in my corner is so energizing and wonderful.