In this instance, the mentality of the consumer is a) "There's not much area to cover so I can afford to put a higher-priced product on the backsplash;" b) the stone counter is usually monolithic so you can use highly decorative tiles on the backsplash (translation: higher-priced tiles); or c) "If I'm going to spend all this money on the stone counter, I NEED a more expensive tile to complement the stone!"
Whatever the thinking, the pairing of tiles and stone continues to enchant the consumer.