In traditional project management, the success and failure of projects are governed by the achievement of the triple constraints of time, cost and scope. Based on this one define the flexibility matrix. What is negotiable and what is not negotiable in Scrum. In scrum projects cost and scope are negotiable where as time is not. What is the actual impact of that on projects;
The first and foremost thing is, all scrum ceremonies must start and complete on time. For instance, all daily standup meetings must start and complete on time. So is the case with the sprint, daily scrum, sprint reviews and sprint retrospectives.
If you cannot buy into the non negotiability of time aspect, do not get into scrum please.