I personally just hate the mage class, lol.
But yes, if you sit down and think about what class is best suited as a starting class, so you can do either pve or pvp. Well that class needs heals of some kind, so pally, priest, shaman, druid or maybe warlock. You also want them to have a bit of survivability so cloth is out. Plus, what class stacks better with multiple of it's self? Priest, other than having them different specs, don't stack at all. Druids can stack, but once again you need different specs. Pally's can stack, but.... we all know pally DPS is a joke, and they have to be melee, or lolshock spec.... (yah....) Now shamans, totems stack awesomely. They have pretty close to the direct target damage of a mage, though no CC or aoe.
I say it's not so much that we are all jumping on the band wagon, but more than ellay picked one of the best starter classes for keeping it simple, while still having fun and learning a lot.
Plus I wanted to roll a shaman for my next class, lol.