Take your dog out to the beach on a hot sunny day without having to worry about them going blind from staring into the sun, when you're lounging away on a towel, reading a book, with your nice tinted sunglasses. You're just so damn selfish sometimes. Or maybe you want to take your dog on a motorcycle with you, because apparently that's a thing, just make sure their eyes are protected though, not that their safely attached to your motorcycle or anything...