We already did migrate to that license: (A)GPLv3+. You can use my code if-and-only-if you won't then hoard your own changes from the world and lock users of your derivative software away from having the same empowerment you did. It isn't about "expectation of gains", and that's a ridiculous way of portraying the situation: it is about a social contract that happens to be enforced by copyright.
And, as such, when your favorite AI generates code similar to my code after having read my code, that's infringement, the same as if a human had done the same thing... only, the AI doesn't bother to consider that angle, and, even if you know to care, you have no way to know what is going on, in the way a human at least usually can know when it is cribbing off of what it knows (though even a human can do this accidentally).
And, as such, when your favorite AI generates code similar to my code after having read my code, that's infringement, the same as if a human had done the same thing... only, the AI doesn't bother to consider that angle, and, even if you know to care, you have no way to know what is going on, in the way a human at least usually can know when it is cribbing off of what it knows (though even a human can do this accidentally).