Just Not Practical?
Maybe, but Bruges has established short-break appeal well in excess of several destinations which do consistently fill 140+ seats for EZY and RYR. The well-known attractions of Bruges itself, and the historical interest in the nearby [Ypres/Iepers] WW1 battlefields (particularly in this important anniversary year) drive a steady market. Of course, 2014-2018 will see a sequence of important WW1 Centenaries which should prompt additional tourist interest. Ghent and the coastal resorts near Ostend are also attractive options for visitors, if less well known.
Given that RYR/EZY have successfully generated tourism booms to some quite surprising citybreak destinations, there is no reason why the area surrounding an established favourite such as Bruges cannot perform at least as well.