I think it's not just the output. I can buy an image on any stock Plattform, print it on a T-Shirt, wear it myself or gift it to somebody. But if I want to sell T-Shirts using that image I need a commercial licence - even if I alter the original image extensivly or combine it with other assets to create something new. It's not exactly the same thing but openAI and other companies certainly use copyrighted material to create and improve commercial products. So this doesn't seem the same kind of usage an avarage joe buys a book for.