Because the output you get can have hallucinations, which don’t happen with a deterministic tool. Furthermore, by getting the `jq` command you get something which is reusable, fast, offline, local, doesn’t send your data to a third-party, doesn’t waste a bunch of tokens, … Using an LLM to filter the data is worse in every metric.

Because the input might be sensitive.

Because the input might be huge.

Because there is a risk of getting hallucinations in the output.

Isn't this obvious?

You really need to go and learn about the concept of determinism and why for some tasks we need and want deterministic solutions.

It's an important idea in computer science. Go and learn.