I think it's sort of a case of "if I have to mobilize these guys, I've probably already lost", where you are still better off reanimating Priests, then perhaps just summoning a single King now and then, as thug chassis, or as leader/buffer for a batch of chariots moving out to the field.
Of course, if you had a convoluted strategy that considered the usefulness of the chariots to be marginalized by late game, perhaps you want all the Kings you can get your hands on, so that they can be geared and deployed at the "Opportune Moment". I honestly haven't studied their full game enough to discover whether that train of thought has merit or not. I guess it just depends on if the Kinfs, with appropriate gear, are en mass more effective than a nearly infinite flow of chariots - and depends on your ability to even forge enough of the gear you want.
Oh decisions decisions.
