"Let's go with the fax machine-y technology..." and the rest of the meeting attendees signed off? Perhaps the brand manager was on holiday? :)
p.s Put another way, I was waiting for the 15 and the USB-C. I'm not going to spend $800 on a device w/ USB 2.0, and I'm not going to spend $1000 just to get what is also a relatively dated technology (i.e., USB 3.0). Which is kinda funny...we're debating the value of USB 2.0 and USB 3.0 isn't exactly the current standard either.
Yeah, I get it. I'm an edge case. Most people don't care. I simply find it hard to believe that Apple so willing cut corners - for no reason - on the flagship devices.
Is this purely kind of on general principles, or do you have a specific use-case for USB 3.0? Because if you do, well, yeah, fair enough, you're an edge-case, but it's worth remembering that most users do not; most people never plug their phone into a computer these days, except perhaps to charge it.
Instead of assuming the millions of customers are deluding themselves into a worse experience, consider that they don't care for this particular feature, and the median user does not need it or think about it at all.
For most people, the cable is a means to keep their battery full. That's it.
The percentage of Apple customers who know you can transfer data over Lightning is minuscule, and of that minuscule number, a further minuscule percentage will care about USB 2.0 vs USB 3.0. A vanishingly small number of people care about this.