Why would I want to do that? I'm rarely ingesting arbitrary JSON. Rather I'm designing my data structures in a sensible way and then maybe serializing them to JSON. Just because JSON can represent heterogenous lists doesn't mean it is a good idea to use heterogenous lists in my programs.
The JSON spec does not require a schema. If you want to write a library that can support any valid JSON you have little options. That's useful if you are implementing something like jq just to give an example.