If you consume power over USB-C, 2 resistor are enough.
But for providing power over USB-C, you generally need a dedicated IC to handle VBUS switching. It wasn't worth it.
Also, once you ship a consumer product with a USB port on it, you'll realize a lot of people really don't understand how USB works, and USB-C doubly so. Square holes for square pegs goes a long way.
Sure, but your power input should be a USB-C. No reason to use the clunky USB-B for that. Labeling as Power In and leaving a regular USB A for the output seems fine to me. Given that most older keyboards use USB-B for their input, A is a perfectly fine solution and solves the “input vs output”.
OP mentioned in another comment that a decent chunk of users is elderly, and C-to-B cables (albeit rare) do exist, so confusion isn't impossible.
I personally really don't like it in a world where everyone has USB-C power bricks readily available and USB-B cables are dying out, but considering the user base it is not an entirely unreasonable design decision - for now.