The problem is why do I accept ai generated PR if I can generate myself?

because you didn't have to take the time to? the friction point is the review, but it's not THAT much different from the old times. you always have the option to develop communal (or private) software on your own; indeed, it is substantially easier now. but that doesn't mean the value of other humans (or human augmented systems, lol) doing work (in good faith) for you for free goes away?