Yes, of course USB-C would have been better. But their greed is constantly pushing them into vendor-proprietary connectors and non-standard solutions in general, and usually it works out (for them). It keeps their customers locked in, be that with peripherals, applications, iMessage, FaceTime, whatever.
This time it's biting them in the *** and they rightfully look like fools selling the latest iPhone and the latest Macbook (Pro or otherwise) with no out-of-the-box connectivity solution.
By the way, while you might be right that a lightning port on the Macbook, with the appropriate 3.5mm dongle (supplied or sold separately) wouldn't technically impact the average user, this move would had virtually guaranteed that Apple would become a laughing stock on forums, reviews, etc. That's not cool, and cool is important when selling stuff based on perceived coolness. And this would impact their average user, who pays the Apple tax to look cool.
