It's also significantly stronger. The lightning connector is male on the cable and female on the device whereas USB-C has a female connection on the end of the cable and is more prone to damaging the male port on the device.
I think another good argument for phones is that it's surely much easier to clean lint out of a lightning port than a USB C port.
Edit: But probably, I'd guess, right now the main reason Apple has stuck to lightning to whatever extent it is is because it's more convenient for its customers. USB C is already the standard, and Apple would benefit from switching to USB C across its product line if its customers would like that more.
if you lay them down on the table and look from up top, they would be roughly similar. In terms of height (if you orient both of them directly towards your face, like you are about to plug them into your eyeballs, and measure the y-axis), I believe that lightning cable is about half the size of usb-c. Lightning also feels much lighter (no pun intended).
