> JSON is lists of lists of any length and groups of key/value pairs
The "top-level" structure of JSON is usually an object, but it can be a list.
> JSON fundamentally IS made to represent tabular data
No, it's really not. It's made to represent objects consisting of a few primitive types and exactly two aggregate types: lists and objects. It's a textual representation of the JavaScript data model and even has "Object" in the name.
> Why make it able to represent tabular data if that's not an intended use?
It's mostly a question of specialization and ergonomics, which was my original point. You can represent tabular data using JSON (as you can in JavaScript), but it was not made for it. Anything that can represent """data""" and at least 2 nesting levels of arbitrary-length sequences can represent tabular data, which is basically every data format ever regardless of how awkward actually working with it may be.