Text is a visual pattern that we recognize just like an icon. When we read "Save" or "Format" from a menu, we're not processing and deciphering that text. We recognize the word just as instantaneously as we recognize a stop sign. Within limits, different fonts and colors do nothing to impede our recognition because we're only working with 26 basic building blocks (letters). Once we "learn" a new word -- that is, once the word becomes visual symbol in our minds rather than a string of letters to be interpreted -- we instantly recognize it in any application that displays it in a menu.
Icons, however, are not made up of universal building blocks. They do not become instantaneously recognizable symbols until we learn them. Sure, we all recognize the universal Save disk or Paste clipboard that most every application uses. But what about Archive? Merge? Format? Uncomment? Outside of a few universal icons, every app is different, and until we learn that app's symbology we're wasting time interpreting (or worse, looking up) the icons. For. Every. Single. App. We. Use.
So why use icons at all? They save space, save time (fewer mouse clicks), and CAN be easily recognizable -- but only if we take the time to learn them. I don't want to bother when I already recognize a symbol for the same thing -- a one-word description of the task.
Symbols made up of 26 basic building blocks which I already recognize, and which can be unambiguously interpreted when I don't recognize the symbol as a whole? Win.
Symbols made up of arbitrary lines, curves and colors that I need to learn for each app? Epic fail.