Why does ARA plugin need to be in separate ARA directory?

I don’t understand why my ARA+VST3 plugin has to be copied to both the VST3 and ARA directories/folders. Why not just use the VST3 plugin in the VST3 folder? It contains the ARA factory, and is how Studio One does it. Can’t Cubase just open the plugin from there, and then call the ARA factory code?