I hate barrel jacks, it seems that every single time I encounter one it's different from any adaptor I have. Size, voltage, and polarity can all differ. People got sick of having 10 differnet power adatpters to charge stuff. Hence the demand for "single connector" which seems to have converged on the USB-C form factor.
Right, but if it's not actually USB-C, at best you're looking at the device not working when plugged into a proper USB-C power supply. At worst you're facing fried electronics.
Agreed that would be like wiring a standard North American household wall outlet with 240VAC. Technically possible, but will probably fry anything not expecting it.