It does not make sense to use it in games. It would need a good synthesis engine plus samples which consumes much more CPU than reproducing a MP3.

If in your game you go the synthesis mode (chiptunes and whatnot) MIDI is a comunication protocol between devices.. if you want to use it to communicate a game with its own synthesis engine it makes less sense. Buy you may want MIDI so you compose in a standard music composing program.

It is used also in other areas that need automation, as lighting (DMX).

But I agree it would be nice to have better examples.