Why can't we make ghost in create of sim ?

I'm not interested in CAS ghosts until they make ghosts make sense. Why do they have hunger and bladder need? To me, ghosts should only have three needs: fun, social and energy. The energy needs to be a special "spectral energy" that works differently from mortal body energy. They should have their own unique way of recharging it, sort of like the way vampires can use dark meditation to recharge vampiric energy.