Unless the revolutionary threat is present, the existing institutions are resistant to transformation. When you have politicians - no matter what they represent - enter into the state, they're going to be severely constrained by what the state makes possible. And the state doesn't make anything but minor modifications within the existing reality possible. If you have that revolutionary challenge outside of the state... then you have the level of social challenge to the existing order that makes it possible to see those changes which really do improve people's lives.