Comment by badsectoracula

For the same reason GenAI output isn't copyrightable regardless of how much time you spend tweaking your prompts.

Also i'm pretty sure none of the AI companies would really want to touch the concept of having the copyright of source data affect the weight's own copyright, considering all of them pretty much hoover up the entire Internet without caring about those copyrights (and IMO trying to claim that they should be able to ignore the copyrights of training data and also that the GenAI output is not under copyright but at the same trying trying to claim copyright for the weights is dishonest, if not outright leechy).