Most people can't even imagine the complexity it would require to actually build a system that correctly tracks down the sources for image generation. Not to mention that each image is generated from literally every single training image in a very small percentage.

It's not hard when someone inputs "create in style of studio ghibli" to say that studio Ghibli should get a cut. It's very different when you don't specify the source for the origin style.

And if you tried to identify the source material owner, the percentage of the output image that their work contributed to would be extremely - if not infinitely - small. You'd get minuscule payouts.