Scheme is used, but people are not in-your-face about it. You might have several implementations on your computer and not know about it. Got a Mac or a Steelseries headset? You got a Scheme. Does *anyone* know what Cisco uses Chez for?
Less glorious, but supporting the point above: "TinyScheme was used as the core of Direct Revenue's adware, making it the world's most widely distributed Scheme runtime."