WHM/BLM still has niche uses.
Although I consider WHM/sch far superior in performance, I spend most of my time on WHM/blm these days. Why? Because I'm mostly a casual player now, who runs around doing minor quests, crafting, farming, and some lightweight activities. WHM/blm is possibly the best inter-zone traveling combo in the game.
Mobility is much more important than optimum performance for me, under normal circumstances. As a result, if I get the occasional help request from a friend who just popped some NM and needs me ASAP, that's what I'll likely end up coming as, unless they're willing to burn a few moments for me to change subjob.
Or if they just need some casual assistance, in which case changing subjob isn't worth the bother (by casual, I mean the sort of "15 second fight, come naked if you want" that seems to be in a lot of storyline quests nowadays). It's only when I know I have something high-intensity coming up that I set /sch.