We don’t do retros because everything is awesome!

I don't think it works that way

The team had an excellent Sprint. They reached all their goals and stakeholders are happy. Everyone in the team has a smile on their face. And then someone says what everyone is thinking:

“Cool, perfect Sprint, we don’t need a retro!”

I see this can be tempting, but it’s not this simple. How do they know there’s nothing to improve?