Is it to provide some common sense in day to day operations? Would you rather the passengers just checked in the baggage as entitled and paid for, so it could fly ZRH-GVA-ZRH, taking precious team's attention with transferring, loading, unloading + rinse&repeat?
The passenger intended result might actually make the ground ops operation much, much easier (especially if the luggage get's mishandled along the way) if they applied some logic, or customer facing imitative.