The question was, why would a system tipping be better than a system of flat, honest fees for delivery. It does not address that to say, within this system, you should do this.

You were giving justifications at a system level, which why I said it would imply that other systems should shift to "pay what you feel like", irrespective of which ones currently use it.

And it's not an exchange, if one side has nothing to withhold, but a gift.