So you believe it's easier to learn which combination of letters in the context of a given interface means "home" or "chat" than an icon? You don't understand how the human brain works, it's much quicker to discern an icon as you glance at a screen then find a word and get your brain to interpret their meaning. There are 26 letters in the English alphabet, an enormous amount of dictionary words, but it very unusual to have a single screen containing more than 10 different icons.