Generative Design & Inability to Apply Simulate Load Cases

Why does Creo Generative design not allow the same flexibility in terms of loads on a part? I need to apply a load that I can apply in Creo Simulate, but there does not seem to be an option in Generative to apply a load as a function of coordinates, to use control volumes etc. I also seem to be limited to a Cartesian coordinate system where I require a cylindrical one. I this functionality exists, it certainly is not intuitive and user-friendly.