since the switch to lightning there is an even larger number of devices and docks all designed around lightning and very few of their customers wanted or asked for usb-c
It’s no surprise that for iPhones, with that large eco system they just didn’t change, while for iPads and macs they did because there just isn’t the same amount of accessories and usb a <> usb c is easy. You can’t use lightning dock devices with usd c at all. It’s far from as simple as “use a new cable” when the device is designed to fit over the base of the iPhone and plug in.
Otherwise they would have incentive to use usb c already as it’s been on iPads and many of their other devices for years and why keep around a separate set of product skus and parts just for iPhone?
So they simply waited to be forced to do it so now their customers will get mad at the eu and not them