The dark is great for hiding stuff and keeping it secret, and obviously there’s a big overlap between “games that use the dark to make things secret” and “games that use the dark to make things scary”. Touch Scary Things only works because the dark signals scariness and also conceals the fact that the scary things are toys, kiwifruit and socks. All the Oh No, Someone Might Totally Be Standing Right In Front Of You About To Do Something Alarming-style games, again, use the dark as a way to hide information, and the fact that the dark is scary is partly a result of the fact that that it keeps things secret.
But the dark is also handy for hiding information independent of any desire to be scary. Waldschattenspiel, pictured above, is a board game where children hide tiny wooden “dwarves” behind boardgame trees, and an adult has to move a candle around to try to reveal them. You need a really dark room for this to work: generally, players report that the adult can see the dwarves a bit, and slightly pretends not to, in order to make the game work. But even when that’s the case, the darkness is still being used to hide information: the fact that the adult knows perfectly well where the dwarves are.