OLBA18 - It's mostly for a mixture of comfort and for the purposes of complying with ETOPS requirements for floatation rafts ( and the pax capacity thereof ) - though pax throuput at the small airport at YDF and crew duty day do have their part to play.
You might be interested to know that Astraeus regularly operate with 148 pax ( i.e. full ) to Aswan, i.e. there and back on a two sector day, which is a flight which is actually longer than is LGW to Deer Lake, e.g. the Great Circle Route Distances are as follows:
- LGW- Deer Lake (YDF / CYDF) = 2144 Nm
- LGW- Aswan ( ASW / HESN) = 2230 Nm
Aside – I can't remember my own flight time length record for LGW-ASW ( aboard the B737-700 ) but I do seem to recall that it's quite a bit over six hours flying time.