iPhone notification tones are part of Apple's default alert sounds, designed to be short, clear and easy to notice without being intrusive. As iPhones became common worldwide, the ding became instantly recognisable even outside the phone itself, and creators began lifting it for short videos, memes and reaction edits. It spread because almost everyone has heard it in real life, so it needs no explanation on screen. That shared familiarity keeps it useful today as a quick shorthand for a message, an update or an interruption.