It's not like other formats don't face similar questions. E.g. if you have a list of key-value pairs to serialize to JSON, do you translate those keys to JSON properties in an object, or do you translate each pair as an object in an array?
The motivation for doing that in JSON comes with best practices: you use the key-value objects thing if and only if you have an ad-hoc list of items that you'd really really like to shove into a well-typed schema.
