Microtransactions for vanity pets and mounts are most definitely microtransactions. You pay money for something in the game. If it has effect on the actual gameplay it would just be a bad way to implement microtransactions.
The thing is that Blizzard has made hundreds of millions on WoW and they are currently encountering a drop in playerbase. The playerbase is still insanely large, but it's a drop nonetheless. Instead of squeezing out every last penny of the remaining playerbase they could probably benefit more by not being such cheapskates and implementing vital features such as this for free.
Why do I call functions like these vital? The competition is implementing these sort of features for free and if they don't want to fall behind they should do so as well.
MMO's are less expensive to maintain than you think these days. In the original days of the genre it might have been necessary to charge a subscription to make it possible for a game to generate profit, but we are far beyond that. I believe Blizzard would be far better off if they started implementing more features like this for free.
