I just don’t think they want a support role at all.
As DPS, it’s easy to gauge your success based on how fast that boss dies.
Tanks are a bit more binary - is everything hitting you and you’re not dying? Good job!
Healers - did anyone die? Nope! Well done. And some minor meter play, as well.
How do you gauge your success as a support? It’s a lot more difficult to “game-ify” a support role. If you’re doing things right, you’ll just have other people that are very pleased with themselves. Maybe you popped a cooldown that resulted in that Rogue doing some crazy damage during a boost window, maybe you spotted a struggling healer and helped to top up their mana, maybe you even debuffed the boss before a tank buster and saved the tank… it’s a relatively thankless job, and WoW’s developers really detest that for whatever reason.
I offered some thoughts on this more than a year ago: Next Hero Class: Dragonsworn? (or: Why Bards, Necromancers and Tinkers Don't Work) 
It’s not that I inherently dislike the other classes that are often offered… I just don’t think they fit with WoW’s current iteration. And yes, I do often push a pro-dragon agenda.
My read of the current team is that they really want to forge their own path. Odds are, whatever the next class is, whatever it is, it’s going to subvert all of our hopes and expectations, for better or worse.