Unfortunately, as of the time of writing (October of 2014) there is no way to prevent FMOD Studio from adding 3D Panner effects to events. Even in entirely 2D games, the desire to attenuate sounds based on distance and direction makes them a nearly ubiquitous requirement for most projects.
That said, if your project doesn’t need them, they can easily be removed en masse by multiselecting all of your events and using Studio’s bulk edit feature to delete the 3D Panner effect from all your events’ master tracks at once. You will need to repeat the process for any new events you add. Remember that you can press ‘Tab’ to cycle through which of the events in a multi selection is currently active.
Hi halfasemitone, there will be a very small amount of memory saving as a result of removing the effect and negligible cpu savings unless you are mixing large amounts of mono sounds (the 3D Panner will upmix to stereo). It’s still best to remove the effect if you don’t intend to use it in your event.