Because it wasn’t created by a human being.

If I ask an artist to create a work, the artist owns authorship of that work, no matter how long I spent discussing the particulars of the work with them. Hours? Days? Months? Doesn’t matter. They may choose to share or reassign some or all of the rights that go with that, but initial authorship resides with them. Why should that change if that discussion is happening not with an artist, but with an AI?

The only change is that, not being a human being, an AI cannot hold copyright. Which means a work created by an AI is not copyrightable. The prompter owns the prompt, not the final result.

So what you’re saying is that the AI is the artist, not the prompter. The AI is performing the labor of creating the work, at the request of the prompter, like the hypothetical art student you mentioned did, and the prompter is not the creator any more than I would be if I kindly asked an art student to paint me a picture.

In which case, the AI is the thing that gets the authorial credit, not the prompter. And since AI is not a person, anything it authors cannot be subjected to copyright, just like when that monkey took a selfie.

Yo dawg…