Indeed... I once had a rather sarcastic passenger who was very critical that we were flying a 767 to GVA around the time of the snow disruption at the start of this year... with only about 50 passengers total on it...

When I got a mouthful of green ethics from him... I asked him how the 250 passengers waiting for the aircraft to arrive in GVA would feel if we did not bring it out with us...

There are many many factors taken into account when the difficult decision to cancel a service is made. Normal day to day ops will include several sectors are very empty flights.

As others have said, don't worry about it.