Yeah sure, no need for state in a CRUD API. But while it is the most common use case for PHP applications (well actually for application written in scripting languages working with http servers), it's not the only use case.

When the only place where you can put state is the database then every piece of state is written in the database. Which lead to intelligent individuals (no pun/offense intended) to write clever piece of infra such as Redis. The truth is, for 10 Redis deployment there's 7 (8? 6? Well, a substantial part) where a long living process holding little state would have done the trick. Now you need to deploy, maintain and scale Redis too.