But why would I ever want to listen something generated by someone else when I can just generate infinite amount of the same stuff myself?

Because it sounds good, you can do both.

But what's the point of spending time and thought for music prompted by others? What I can generate sounds exactly as good and has the exact same value...

Can’t you say the same thing about why listen to human jazz musicians?

I am not a jazz musician. I can't generate their music, all the nuances, the improvisation or the feeling... in other words the human factor of their craft 1 to 1 with a press of a button.