Why do -carrying- AP supports still have to ward?
Okay, so supposing you're in a game. Your top is 0/10, your mid is 2/5, but your botlane is going on a killing frenzy. They are dishing out the damage- your support in particular.
Now it's not top's fault. They've been counterpicked. But your 7/0 Morgana just strolled top and solokilled the fed enemy toplaner with ease. Her kit just happens to be perfect for the enemy team. She has huge combat effectiveness in this particular game, whilst your toplaner has none and has very little chance of gaining any.
Why do we not designate Morganna the 'carry' at this point, and ward to protect her? Why is she still protecting us? Why are we making it so easy for the enemy team to take out our strongest player by sending them to do the warding? Is there a reason?
(And I'm aware vision requires stacking time now. It does require time to switch over who is warding, but that does not render it impossible. Moreover this isn't a tactic that only started with this patch)