AC/DC Power adapter plug: difference between center positive/negative
Some manufacturers decide to make their power supply "unique" to them and to that end, they also use different sizes or types.

The Apple magnetic series (magsafe) is a good example, while they use multiple terminals to identify the type of battery capacity and the correct charge rate, it is unique to Apple.

Much the same as the mains plugs - every country thinks that theirs is the "best" system... UK has 3 pin, but the EU uses either two or 3 pin, both of which fit in the same socket.