Because it's barely been a year since we've gone from people confidently asserting that AI won't be able to produce visual art on the level of human professionals at all to the current situation. Predictions on ways in which AI performance will not catch up to or overtake human performance have a bad track record at the moment, and it has not been long enough to even suspect that the current increase in performance might be plateauing. Cutting-edge image generation AI appears to often imitate human artists in obvious ways now, but it seems quite plausible that the gap between this and being "original"/as non-obvious in your imitation of other humans as those high-performing human artists that are considered to be original is merely quantitative and will be closed soon enough.
> You mean that any artist should be just happy that his work is used by other people / rich corporation / AI without consent? Cool, cool.
I don't know how you get that out of what I said. Rather, I'm claiming that artists will have enough to be unhappy about being obsoleted, and the current direction of their ire at being "copied" by AI may be a misdirection of effort, much as if makers of horse-drawn carriages had tried to forestall the demise of their profession by complaining that the design of the Ford Model T was ripped off of theirs (instead of, I don't know, lobbying to ban combustion engines altogether, or sponsoring Amish proselytism).