Of all the things that inhibit our use of programs, icons are surely the least because after you've pressed them a couple thousand times, I hope you still don't forget them. Text takes up a lot of space.
That isn't what we see with most web apps these days, including the major ones. There's continual change, including the icons that are used, where they're positioned, and what happens when they're clicked on. If you discover what an icon means and does today, there's a very good chance it'll have changed by tomorrow, if it's even still around.
We're much better off losing a small amount of space, but getting an obvious and unambiguous description when text is used instead of icons.
Text works just fine in most applications, because the shape of a particular word is itself iconography.