The Ipad Pro is usb 3.0 compliant IIRC, because it has double the amount of pins that the iphone has. It is not a problem with the cable itself, I agree. But it could easily (and cheaply) be implemented for all iphones. Maybe it was gimped on purpose to push airdrop, and to "make everything wireless" agenda.
And I mention dongles, as not everything previously stated, will require a dongle. You can use a usb type c cable as an Ethernet cable (more than likely rare case scenario, nonetheless, but still a possibility). You can also plug a phone into a display to charge the phone, while mirroring the content to the display. I can plug my phone, into my tablet via just a usb type c to type c cable, and charge my phone, or vise versa. There are so many possibilities with Usb type C, that lightning cable, just can't do.
And there probably won't be any non-headphone jack, high impedance headphones for some time, until headphone manufacturers are pushed to go that route. Which may not happen anytime soon, because most fall into the high end category. But let's just say they do exist. Why would lightning be superior for sound to usb type c? Simply put, It wouldn't. Apple doesn't support as many of the audio codecs and bit rates that the rest of the world supports. You can see this in the iphone, apple tv, homepod, etc. Usb type C is standard, while only apple uses lightning. Manufacturers would jump on board to support an open standard platform, than put themselves in a restricted ecosystem.