DC Connector Standards
Skimming this 1998 article on in-seat power standards for airplanes will give you some understanding for why marketing types should never be allowed to make engineering decisions.
The article points out the absurdity of specifying 15V as the standard for laptop power outlets on airplanes, when most laptops use 18–24V. Given that airplanes already have 28V power systems, it would have made far more sense to just spit out 28V through the power connectors, thus allowing for very inexpensive, small power adapters to be offered for any laptop (or even built into them).
But the bottom of the article is also interesting reading, for I learned there is a standard specification (ANSI/SAE J563) for cigarette lighter sockets—and it has not two, but three different size specifications. The article also explains all the problems that using these connectors for powering electrical devices (instead of cigarette lighters) have.
