It's always surprised me that FR's requirements for 738 landing lengths have been so high. Here in JER, we have a runway of around 5,500', give or take; 738s have operated here (Excel and Hapag Lloyd, to name two) and on considerably longer flights than FR would operate. Moreover, by getting into the more peripheral places (which may have shorter runways), but where it may be the only operator - certainly of the major carriers - it creates new markets for itself. Put another way, the longer their runway requirements, the more airports they put outside their radar scope and for a carrier which prides itself on getting into the most peripheral, back of beyond airports, that's possibly not a good thing.
If you're going to spend $40m on a new airplane, why not make sure you make it work as hard for you as it possibly can and that means using its short field performance; it's a 737 after all - a big 737, but still a 737 and short field performance is part of its mission.