Apple peripherals use lightning, and Apple doesn’t seem to be willing to change that policy.

Main devices uses usb-c, so a lightning to usb-a cable, would not be appropriate.

we know from tear-downs that the previous magic keyboard uses the same charging IC as some other apple devices, so it’s likely something to do with using existing manufacturing processes to save on cost. that’s just a guess, though — it’s hard to say for sure without seeing someone dissect one of these (or knowing exactly how they’re made).

Yes, because there’s no benefit to their business to invest time switching it to USB-C, and significant upsides to existing customers if they continue using Lightning.

What use case do you envision should be higher priority to Apple’s customers than being able to recharge their keyboard, trackpad, and phone from a single Lightning cable left plugged into their desktop computer’s USB port?

This is indeed inexplicable