From this article on Strickland's player page about who would hate robot umps:
I never considered that. With no one on, catchers can just take the stress off their knees and just not catch the ball. A large reason why I dislike the auto intentional walk is because I just find it...weird and awkward. How weird and awkward would it be to just see a pitcher throwing to no one?
Maybe they'd have to change the rule so that the ball must be caught to confirm a strike, I suppose, but robo umps sound ideal until you dig a bit and determine it isn't as clear cut as it seems.