Virginblue,
Yes i would agree but have you done the Bristol City center to Manchester City center on a train? or driven/used coach service with the delays on the motoways and both cities center congestion, as with the ASW Route it was well used by the financial and business comunity who would pay a premium rate for the convenience.
With spare a/c sitting on the ground at Bristol it could generate additional revenue (even if it were just once a day within business hours) for the airline and especially as Cornishman said if Bristol was used as a hub with Newquay or Plymouth if they reopen as rumoured, i used this route on numerous occasions and found it excellent.
I know it's contracted but BMIR do run the Bristol - Hawarden service for Bae