No other Apple products include a USB A port. It's to standardize the whole ecosystem on USB C.

Likely so the phone can charge off of a nearby MacBook which has usb C ports.

Probably need usb-c to charge the phone at full speed?

not their computers, also Apple usually pushes changes forward, not backwards, in this case using lightning they just diverged from micro USB, and probably now most people have USB-C chargers

I think most cars nowadays come with USB-C (or a mixture of USB-A and USB-C) ports. Same with chargers and computers.

Cars last decades, so the vast majority of USB ports in cars are USB A.

The last power adapters and cables bundled with iPhones already had USB C connection.

Faster (higher power) charging.

(Current) MacBooks don't have USB-A.