The post you're replying to doesn't mention iOS, just mobile (though it may have been edited). Anyway SQLite is heavily used in Android and well, and other mobile platforms going back to all but the early versions of Symbian even. It's been the standard for address book, calendar, settings, to-do apps, etc for over a decade. A typical smartphone probably contains around half a dozen SQLite DBs right out of the box, which means the building I'm in probably houses several thousand of them. The total number of DBs in the world must be in the tens of billions, just from mobile devices.