People have bitched about being forced to control things that aren't their character in MMOs for decades. I remember people cried like fucking babies about Wintergrasp and them adding vehicles on the forums
"I learned to master my class, now I have to learn something new????"
This is why we can't have nice things
Because its usually implemented in a way thats just fucking worse than your character. Like the Tank in WoW's PVP? Its fucking awful and slow. Sureeeee you can take the wall/tower/barricade out with much more ease. But god forbid one to three or more players start attacking you. Its a gah' damn TANK - why is it some slow, fragile, glass cannon? How is that fun? "Oh but you just need to be a team player!" no.. fuck that. Make it damn near God mode for a short duration. Or the CC from Naxxramas raid boss? Yes, that is exactly what I want to do while everyone else is having fun ... /yawn. Or all the vehicles you can use in Ulduar? Fucking hate starting that raid, but love the rest of it, because I hate that entire beginning sequence. The vehicles are just straight AWFUL. If you want interaction from players like that, then have them interact with the environment on their character - like the saw blade dude in Siege of Orgrimmar where you're hopping in tubes, and traversing conveyor belts etc.
Its just so fucking boring. Worse yet, even the games I have played where its at least implemented to play well and you're almost God mode - its almost required that you do it at that point and time when you're playing the game. You dont have access to it any other time. Unlike say, Halo, you have the tanks and other things - and they are out in the open, optional, powerful, and not necessarily restricted to an area because the barricades can usually be overcame. The only time you cant use them is when the terrain switches to a tunnel. But even then, you can force a speeder up in them usually - which is still powerful in its own right.
TL;DR - Vehicles in MMO's are fucking awful in comparison to other games like Halo, Call of Duty, etc. If people arent fighting/bitching over who gets to "use" the vehicle, then your implementation of them is fucking awful.