Because generative AI has been built off the backs of everyone, whether they consented or not.
This is covered by fair use, and in any case intellectual property is bullshit.
Because AI companies (Nvidia, Facebook, pick a company) have pirated enough material to keep any individual in jail for life, and yet they have no consequences and can profit off everything.
Legally, downloading stuff illegally is a civil content, so you can't in fact go to jail for it, only pay fines. Morally, the whole concept of piracy evolved out of government-granted monopolies and was pushed by rich pricks as a way to get richer at the expense of everyone else, so there's no reason to give it any moral weight.
If generative AI can not be used for commercial purposes, it also cripples the ability to replace artists, writers, etc., with an AI that stole all their work in the first place and is regurgitating it.
"Protecting jobs from competition" is very low on my list of things I want enforced via state violence. Maybe it's high on yours, but I'd like not to get state violence'd to satisfy your sensibilities thank you very much. Otherwise you can't complain when, say, conservatives use state violence so enforce their sensibilities on you.
Take the profit out of it, and we can all (to some degree) benefit from it. Take the profit out of it, and stop them from hoarding and destroying books/knowledge, destroying the environment, destroying your economy.
Uh... what? What's your reasoning there?