[dcosson]

You don’t “need” almost anything, the point of new tools isn’t usually that you need them it’s that they make your life easier.

Apollo Client makes a lot of things about frontend apps easier, which is possible because of the well-defined and typed interface that graphql enforces. No, you don’t need it, and there are other ways (like maybe using Swagger) that you could get similar typing for a REST interface. But, FWIW I’m not familiar with any tools that are quite as comprehensive as Apollo out of the box that don’t use graphql.