Earlier quoted context omitted.
It's quicker to glance at icons and spot the app right away than not read each and every item in a list.
Anyway, I think the idea is to get some visual cue that you're about to tap the right icon. You know where you put your apps on your home screen, so the colors or wahtever lead you there faster. And the icon provides a large touch target. Going back to the original article, it doesn't really matter what the icon looks like, as long as it's unique. You're not looking at each icon and asking yourself "is this a camera?…
Really? Because when I used an iPhone, I most definitely didn't know where most of my apps' icons were. I knew most of them on the first screen and the rest of the screens were a mix of random stuff.