Quick, thirty minute turnarounds and high frequency are not the highest priority of medium-haul tourist class airlines.
Lots of bums on seats and an aircraft that can take lots of palletised freight is much more important i.e. the 767-200/300 is better suited than a 737 with manual 'chuck the bags in' cargo hold and a relatively small amount of seats....Seems to be working just fine for the Ochra folk at Australian Airlines