Because it's an essay of personal experience, and the author's drug, er, device of choice was an iPhone (“iPhone” and “smartphone” are used interchangeably in the body to refer to the author’s device.)
The fact that other people might share similar experiences with other devices, and that the author even recognizes this, doesn't change the fact that the personal experience being addressed relates specifically to an iPhone.
The fact that other people might share similar experiences with other devices, and that the author even recognizes this, doesn't change the fact that the personal experience being addressed relates specifically to an iPhone.