One of the things here is the USB A is limited to 500mA at 5 Volts. USB C can provide far more current and voltage, which gets back to overall load issues, and folks causing the circuit to trip. A coach full of folks charging their phone via USB A is one thing. A coach load of folks running their MacBook laptops powered via USB C is an entirely different thing!
USB-C PD allows the chargers to negotiate what they output - On most multi-output chargers the power actually gets cut to all devices when something new is plugged in and the devices renegotiate - e.g. on my 90W charger the 45W port will only output that with a maximum of two devices connected, connect a forth and it drops to 25W. My Laptop require at 110W charger to fully charge & power itself, but under normal office tasks a 45W charger is sufficient to stop the battery draining, and even a 25W charger will slowly charge it when turned off. USB-C is very flexible in this regard.
Would probably struggle scaling that to coach level, but at pair of seat/table level that sort of thing could work, providing maximum power on your own, dropping down as more devices are attached.
Using USB-C universally (on the railways, buses, taxis, and transport interchanges) would mean that eScooters, hair curlers etc couldn't even be plugged in, while meaning people don't need to carry 3 separate things with them constantly to ensure they can connect it (USB-C to USB-C Cable; USB-C to USB-A Adapter; standard charger).