With a single team you can bootstrap without too much trouble. Even then a good coach will still help you navigate the adoption process.
So why use a coach?
- You want to get going faster
- You want to avoid the mistakes that most people make when they start (Scrummerfall, Command and Control Management)
- You’ve started and don’t know how to deal with the organizational impediments that Agile has revealed
- You want to scale
- You want to recover an “Agile Attempt” that went off the rails
- You want to recover a traditional project that is late and over budget
- You’re struggling to Agile in a hostile environment
The reasons vary with each client, but in my mind, it’s simply that Agile may be easy to describe, but it’s hard to do.
Update: Don Grey and Esther Derby have already written on this topic. Great minds think alike.