It's not. Scrum is a training/introductory agile framework. There is an evolution to scrum built right into the framework that transforms it into not-scrum. The framework encourages moving from the initial (and what most orgs think is the final state of scrum) "Type A" where the team work in isolated timeboxes, with downtime between for planning etc. through "Type B" with preparation(s) for upcoming sprints, and feedback from previous sprints, overlapping the current sprint, to "Type C" with complete "just-in-time process" transformation where doing any given ceremony is done on-demand. And, crucially, it encourages evolving _beyond_ this.
Type C will be familiar to anyone practicing Kanban. Or dare I say, anyone with experience with "doing agile right" will have an experience matching what Type C describes.