Because it has no mechanism for creating novel ideas...

It's like saying a calculator could spontaneously derive its own proof. No it can't, because it has no ability to do that. It physically does not have a way to create new ideas. It cannot reshape its own circuitry like a brain and it does not have spontaneous thoughts.

How do humans come up with novel ideas?

First we need to define ,what creativity and intelligence means ,so we can compare that with human results

I hear what you are saying, but I'm not convinced. Can you dig a bit deeper?

What makes an idea "novel"? What types of physical processes can create new ideas or have spontaneous thoughts, and which can't? What is "special" about brains, in your view?

I'm looking for some meat on the bone here.

ChatGPT is not like other chat bots which operate like a calculator and that is exactly why it is popular. You can put random inputs like "write a short story with 900 words with a bear and wolf about driving to the casino where they win big but can't spend the money" and it will output something total unique based on those inputs.