The switches are only to let also light pass through or bounce off of those shaders. Since caustics can be extremely noisy, even after tons of samples, it makes sense to be able to turn them off. So if you have a scene consisting of high value fresnel to mix between diffuse and glossy based materials, the scene will darken considerably if caustics are turned off as light only bounces of the diffuse shader, and you may want to compensate for that.
Caustics are near impossible to create “caustic patterns”, but can give an indication of what a scene should look like, brightness wise. See this post for good example of this.
Cycles doesn’t have bidirectional path tracing, so finding the lights causing caustics is practically impossible. It’s just not suitable for those tasks.