But it seems like it would be useful nowadays, since some laptop have mostly USB-C connectors, and USB-C to USB-C is pretty common. I’ve never seen a C to Micro. Do they even exist?
I have a Pico in front of me, and there's plenty of room there for a USB-C footprint and the two 5.1k resistors. Given that, I cannot reasonably agree that the "design" stage is significant.
In other words, it's a change that I would make to my own board in 2-5 minutes because the stakes are low. My ballpark guess is that such a change at RPi would have to go through a proposal stage, a PCB change review, and then there would be dozens of places to update documentation.
Since backwards compatibility is non-optional, this would result in a separate SKU, which means that the whole distribution chain needs to be updated with a new product.
So, I acknowledge that when you're working at their scale any change like this is the definition of non-trivial. What I don't agree with is the conclusion that it's not still clearly the right thing to do.
They do, in spades: https://www.amazon.com/3FT-Micro-Data-Charge-Cable/dp/B0DDWH...
I look forward to the day when they're no longer necessary.