We often get asked why Scrum has only 3 roles, 3 artifacts and 3 ceremonies. In fact, our customers simply want to know why Scrum works. In these slides we try to explain the principles behind the prescriptions of Scrum, in the form of 5 Whys: Why Scrum? Why 3 Roles? Why 3 Artifacts? Why 3 Ceremonies? And Why agile engineering practices support Scrum?