The most usual and typical place DRF Serializers turn up is a as a parallel to Django Forms for processing and validating incoming data from a client. However DRF Serializers are far more flexible than most developers realise. They are simply a declarative way to declare the shape of some valid data (before type hints existed.)
Therefore it would be entirely logical to use Serializers to validate data when processing data through an API response to then either save to your database or pass to your clients. Another situation could be serializing data to dump into object storage like S3 or using them to import data via a management command.
Simply put Serializers do not need to be tied to a view to be effective in the management and validation of data.
All that said, pydantic might be a better fit for these use cases in a fresh project, but DRF is a solid option to reuse an existing dependency and have all the nice hooks into Django.