For example a pattern I've seen a few times goes something like this:
* Teams get good at breaking down and estimating backlog items, they tend to all become the same "size" and need about the same amount of "work"
* Product Owners get good at prioritising the work so that the most valuable stories are at the top of the queue
* Dev team and product owner turn have a collaborative relationship rather than a boss-minions relationship.
* The combination of those three factors means that the planning meeting basically turns into "we do the next N stories" where N is the number of stories you get done every sprint. So the utility of this meeting disappears.
* The process of work flowing through the team starts resembling single-piece flow. Everybody works on the next most important thing.
* People start continually delivering, rather that just being able to deliver at the end of the sprint.
* The last two points mean the utility of breaking work into sprints kind of vanishes.
* Everybody notices that they're doing flow-ish things rather than batch sprint-ish things and starts looking to the lean / kanban world for ways to optimise the process further.