Tigers!
There might be other reason, but I'm quite sure I would've left for longer periods if there had been no Tiger forms/illusions for druids/monks!
Now if only SoE would reverse the change to the model that came with AoD. The added fur around the nack/cheeks might be neat in theory, but ingame they really look like glued and rather rigid scraps of paper -> Not Tigress approved! BOO! Wantz old, cuddly model back!