Nintendo is not making a USB-C computer, they're making a _product_ or a cohesive system.
They do not want you plugging in an arbitrary charger (which may not have the right wattage), don't want you laying the switch face up (nubs on the controllers getting in the way), face down (scratching the screen), plugging in a usb-c controller and dragging the spiderweb of wires off the entertainment center, or trying to use the touch screen while attached to a TV.
They wanted a vertical dock that managed airflow, charged at the appropriate rate, and guided you away from asking why you couldn't have some janky setup where you're trying to treat it like a gameboy advance (local screen simultaneous to big TV) being held by kindergarteners who pull the TV off the stand).
...so the dock is effectively a sacrificial buffer/safety system to prevent your switch from causing damage to your TV.
Why not? The standard deals with such a situation fine… There is zero danger, the PD contract wouldn’t be able to negotiate, so the system could just indicate with an LED or a message on the screen or something to show it’s not going to be able to start charging without a bigger charger. This is literally a solved problem.
DS Lite famously had a silly proprietary connector for charging, which required their special wall charger... which was literally a 5V charger. It could have been mini/micro USB from the beginning, but no.
At Nintendo scale, I bet it does though