It’s obvious that JSON Schema has been designed for JSON objects and URL / query parameters aren’t ones.
So I guess that’s “ideological” reason why we can’t use them. However, they could easily make sense (picrel) as long as schema does not describe object.
To being unable to use them those feels like artificial limiting :).
Anyway, it’d be nice to have any way to reuse definitions for those params.
Maybe, UX-wise, creating a distinct space for “primitive schemas” (or sth) constrained to only non-composite types would make this work?