Many, many businesses do not have written plans for the future. And like Sitton and Squyres, many of them are successful. But that doesn't mean that a written plan isn't valuable. They know their industry. But planning is just the most important thing.
Nobody wants to do it.
Wilhelm admits that any three-year plan will change long before the three years are up. There's no doubt about it. But you can change it any time you want. You can throw it in the trash. But you really need to go through the process.