Are there any technical reasons to have the flat contact in the center of the usb socket rather than the plug?
I would guest it’s just for having more surface area to have more pins. An USB-C can have up to 24 of them. Where as Apple’s Lightning 2 connectors have 8.
USB-C connectors are much more than chargers. For example, I can connect two 4k Displays, Power, Ethernet as well as all peripherals (including a couple external harddrives) to my laptop with a single Thunderbolt 4 cable with an USB-C connector.