Last I checked, even WN is scaling back capacity so I wouldn't expect WN (or WestJet) to fly some of these smaller routes served by DC-9's. It's all about matching capacity to load factors and the DC-9 flights I've been on could use some capacity reduction. Believe what you like about WN, but they are not the end-all, be-all solution for travelers. Neither is DL/NW, but anyone who thinks one airline is the end-all, be-all is only fooling themselves.