Seriously imagine the consequences of this "eat or be eaten" approach. What it incentivizes is not feature development per se, but fragmentation for the sake of it. This in turn leads to less attentation toward maintaining the shared base of the fragmented forks, as it has been superseded with features X and Y in different, probably incompatible forks.
My point is that the original maintainer can defuse the forks by including the same features. That leaves users no reason to bother using the forks.