Do we need a Retrospective after each sprint?

Retrospective at the end of each sprint is a formal ceremony in Scrum and is the two out of the three pillar of the EMPIRICAL PROCESS. (Scrum framework is based on Empirical Process). As most teams that are doing Scrum use two weeks sprints and they sometimes wonder if they need to do Retrospective after every sprint?
Here are some common reasons why Scrum teams or management might not want do Retrospectives after each sprint:
1: the team is busy, and the deadline is looming
2: Retrospectives are boring
3: Retrospectives are unproductive
4: we are an excellent team, and we don’t need Retrospective

1: the team is busy, and the deadline is looming

The deadline is very close, and the team needs to be focused on delivering the last few remaining stories. The question most commonly asked: At this extreme time of pressure can we spare 1 hour to do a retrospective? I find that the benefits and impact of doing a Retrospective outperform the time it takes for you to do Retrospective. If you are busy, then you could have a Retro entirely focused on how we can speed up. You might be able to do things in short-term that might help you speed up. You might identify some blockers that are slowing your scrum team down. Maybe using POMODORO be your the saver for the team.
Or you might have a Retrospective on how did we get to this stage in the first place? In my favourite book, The 7 Habits of Highly Effective People. Stephen R. Covey titles the 7th habit, Sharpen the Saw. in this chapter, He talks about a saw man who is very busy and doesn’t stop to sharpen is saw because he is so busy. Over time no matter how hard his work, he is slowing down. If the scrum team don’t take time out to inspect and adapt, learn from things that didn’t go well and things that worked very well. The team will start to slow down no matter how hard they work.

2: Retrospectives are boring

I agree that if you are doing the same retrospectives format every two weeks, then it will get boring so the Scrum master should change the format of the Retrospectives. An excellent resource the Scrum master to make the Retrospectives more productive is a book called “Agile Retrospectives: Making Good Teams Great (Pragmatic Programmers)” by Esther Derby and Diana Larsen. I seriously recommend this book to every Scrum master to read.

3: Retrospectives are unproductive

If the team is finding Retrospectives unproductive, then it is a duty of the Scrum master to make them productive. Scrum Team might find it useful to add the actions from the Retrospectives onto its sprint backlog so they and track to completion. A way to measure the usefulness of the Retrospectives is to do Retrospectives of Retrospectives. It is merely an anonymous way for the team to give feedback to scrum master as to how useful they found the sprint.

4: we are an excellent team, and we don’t need Retrospective

No matter how good the team is, it will always have room for improvement. If the team is truly a great performer, then they would always be trying out new thing and doing experiments. A retrospective is the place where they should be discussing which experiments were useful, what really worked and what didn’t. If the team is not experimenting new ways of doing things, not trying out new techniques, and not trying out new tools then the team will slowly but indeed become a low performing team over time.

Some useful resources

1: A great resource for improving your scrum teams retrospective: http://www.funretrospectives.com
2:
3: