Mirrors are sort of a weird thing. On the one hand, they're often associated with horror and a sense of dread. When we're looking into a mirror it's easy to see a world so similar to our own... and yet removed. Unattainable. Mirrors play a fundamental part in so many urban legends and slumber party pranks, such as Candy Man and Bloody Mary, that they hold a lingering sense of unease in our fragile minds long into adulthood. Something about their simple construction triggers something deep and hidden in our brains that makes us feel watched, observed, judged.
On the other hand, they're how we check out our hair, and take selfies.