I don't think their is a PB preference against them.. so to open with "I wonder if people prefer" is false.

Also the animal theme focus has been brought up in the past and not met with much fanfare from the pb or imms.

I do not think customization is not nessecary for every class, and if limited staff time is going to project development and implementation in regards to customization there are higher priorities than shifter (healer and assassin post edge nerf) that have far less options than shifters.