I guess that they would have used USB-C here too, but the power supply is 143 watts and USB-C only supports 100. As long as they need to use a non-USB-C connector, they might as well make it a nice one.

I think the worse thing is that the iMac needs to ship with a USB-C to Lighting cable in order to charge the terrible Magic Mouse via its ridiculous bottom port that prevents use of the mouse while charging. And even the brand new magic keyboard still charges over Lighting. Lightning needs to die.