It's not really necessary because as you say, there are other ways.

But it's useful if what you want to do is create a simple API to access your data. If your use case includes buildinga CRUD app, or API, you basically get that out of the box.

If you have several components/clients (in different languages) which need to access your database it allows you keep a common interface instead of having to work with different specific libraries/frameworks for each language.

(PostgREST user)