The company talks big about a beautiful vision of multi-purpose cables, carrying power in one direction, data in both directions, etc. They provide one of those cables...but it turns out that it only carries power. So, imagine if your airline was talking about the benefits of brushing your teeth with good toothpaste, and their provided teeth-cleaning kit just has a toothbrush.
Since Apple's shipping a "random USB cable" anyhow, it would make sense for them to ship the version of it that actually does all the things they've been advertising.
The toothbrush has a single purpose. The cable could be used to charge and to transfer data. It can't be used for the second case for no good reason apart of saving a couple bucks per box. I'm pretty sure Jobs wouldn't have it.
Because a lot of people fall asleep on flights, and want to refresh their oral hygiene when waking up, and the airline realizes this extra will be appreciated.
Now, do people need USB-cables when using their electronic devices? And would that little extra be appreciated?
Edit: In case it wasn't obvious to the readers, the reason behind the missing toothbrush and missing USB-C 3.1 cable are the same.
Who the hell expects a toothbrush with their laptop? Or a random USB cable in that matter?