There are many reasons that teams switch from Scrum to Kanban. Some make perfect sense, and some don't. Even when the reason isn't completely sensible, moving to Kanban can still be a positive change.
Common reasons why teams switch from Scrum to Kanban. Teams may have multiple reasons or, seemingly, no reason.
1. They are bored.
2. The team is consistently finishing sprint work before the end of the sprint and pulling in more work.
3. They are primarily a production support team.
4. They are having problems with management, product owners, and other team members that they can't figure out how to solve.
5. They have a separate Tester or Business Analyst who does not do development work.
6. Their formal sprint planning meetings are very quick, as the stories are ready for development and the sprint work has been discussed ahead of time.
7. They are working very closely with their business partners and reviewing sprint work with them immediately.
8. They are releasing often, if not continuously.
9. They are talking about retrospective items outside of a formal retrospective, and solving the issues or setting up the experiments whenever needed.
The first question to ask the team is: "What is the problem we are trying to solve?" The second is, "Is this the best way to solve the problem?" If so, or even if the team can't come to a conclusion, there's no harm in the team try Kanban for a short time to see if it's a good fit. Tools like Jira can run a Scrum board and a Kanban board over the same project, so switching back and forth is easy.
Being able to change frameworks, practices, and processes is a big step in a team becoming truly autonomous.