But they are not duplicating or distributing it. The whole point is that the AI is just reading and learning from it, just like a human would do.
For a more direct counterexample, I can memorize something and type it back out, but if it is copyrighted the law doesn’t make an exception just because it passed through my head.
I do agree that we should encourage human creativity. But if AI isn't making copies, and the output of AI isn't awarded copyright (as is currently the case) then I think humans still have sufficient reward.