No reason for USB-C on the iPhone itself. What people want is rather the included cable and power adapter to have USB-C instead of USB-A so the iPhone can work with all the latest MacBooks out of the box.
So yes, USB-C should replace USB-A side, but there’s no rhyme nor reason why it should replace lightning. USB-C as a standard is a mess. Take USB-C audio, there’s a huge compatibility problem on USB-C headphones on Android to the point that some Android OEMs are reverting back to 3.5mm jack. Why do we want that? Lightning is more straightforward and already have an existing ecosystem. Plus USB-C is much larger than lightning, which makes no sense in a small device like iPhone.
So yes to USB-C replacing USB-A (long overdue), but no to USB-C replacing lightning.
Oh, and I have yet to break a lightning cable, even the original one that came with my iPhone 5 is still good. Not sure how people treat their cables that they have to replace it constantly.