If you're unlucky it could happen that if another (ex LPL) flight, with a full load, developed a technical problem, operations might make the decision to substitute it with your, lightly loaded, flight's aircraft and consequently cancel your flight. It happens, but not very often. Of course, this would only be the case if the return sector for your a/c was also light. As already mentioned, a light load outbound doesn't mean it's the same for the return sector.