#15 - June 26, 2014, 9:32 p.m.
Because they were looking pretty outdated, of course. While our environment art gets better and better, dungeons and raids have higher fidelity, zones have more detail, as we update models for prominent heroes, introduce new enemies and bosses with high polys and high res textures, etc. etc. the old character models just look worse and worse by comparison. It was past due, really. But you are right, it's an enormous undertaking, and one our artists are extremely passionate about.
But, to respond to your point about armor, yes that's true armor can cover a lot, but plenty of people do like to play with their helmet turned off--and it's nice to have a pretty face showing. But also the basic upgrade of polygon count and animation detail will have an effect all of the time, regardless of armor. Plus, updated character models are a shot-in-the-arm for any machinima makers out there looking to cut together WoW footage. Oh, and also, probably not super obvious but a lot of armor is actually just a texture directly on the geometry of the character. Any increase to the polys of that geometry can have a direct benefit to the way armor looks, new and old. And also now we can design gear to show off the male human high res nipples/chest hair. If we were so inclined.