What is the advantage of specifying the version in Rest Controller (Java Spring)?

Question

Java

I am studying the technology of creating Rest API using Spring Boot. Many developers recommend putting a version number on each controller (Example - RestControllerV1). This rule in the existence of version control systems is confusing.
Why is this good manners and what benefits does it provide? Customers are constantly changing requirements, so there must be multiple versions of the same controller?
I would be very grateful if you share your practical experience.

Answer 1

Advantage of backward compatibility with client applications. Upgrading your service won't break everything for users who haven't upgraded yet.