Zwift currently chooses the best set of effects that your current hardware can comfortably run. It only shows in the settings the ones your graphics card can support without the frame rate dipping to the point where Zwift just performs too poorly. Currently I think you get the basic graphics and effects first and then the better video cards just provide more “luxury” options such as sunset lighting effects, a head light when it gets dark etc, so if you don’t have those more “luxury” effects now, then having the option to switch them on is just going to result in too low frame rates and very poor performance. Making these options available to people who have no idea of the effects they will have on how the game will run would only lead to a whole lot of complaints and extra trouble for the support team. For those who want to fiddle there are hacks to be found if you do an internet search.