While there's some truth to that, I'm not aware of a de-facto standard 12V connector.
I guess SATA power could be interesting as it has 12V, 5V and 3.3V rails, but I don't think it's designed to withstand as many plug cycles as USB.
Firewire can supply power at 12V, but that's not standardised, so no device can rely on it.
Many devices use 12V, but they use a vast spectrum of different plugs and sockets - many are coaxial power connectors of different shapes and sizes, some are not. USB is a surprisingly good choice, as it's standardised at 5V with a minimum of 100mA and the option to draw up to 500mA. It's also vastly more popular than any other similar connector.
I'd say the closest thing we have a 12v standard is the barrel plug used in a car cigarette lighter port. Of course, that's a pretty ugly solution for an outlet.
I guess SATA power could be interesting as it has 12V, 5V and 3.3V rails, but I don't think it's designed to withstand as many plug cycles as USB.
Firewire can supply power at 12V, but that's not standardised, so no device can rely on it.
Many devices use 12V, but they use a vast spectrum of different plugs and sockets - many are coaxial power connectors of different shapes and sizes, some are not. USB is a surprisingly good choice, as it's standardised at 5V with a minimum of 100mA and the option to draw up to 500mA. It's also vastly more popular than any other similar connector.