This is a bit confusing, since JSON data commonly has an implicit schema, or "deep type system" as this post calls it, and if you consume data in any statically-typed language you will materialise the implicit "deep" types in your host language

That is an incredibly expensive operation to perform. Being able to look at two binary blobs of data and quickly determining whether or not they are the same type of data unlocks a whole host of functionality over large amounts of data that is otherwise prohibitively expensive and slow.