I was watching my young nieces (2 and 4) playing with the iPad, as children are known to gravitate to, and noticed that they stop dead in their tracks whenever they encounter a word, or an icon or symbol that they don't recognize. It dawned on me that they are illiterate in the language of WIMP in the same way that they are illiterate in English. What WIMP is is a visual language that they have yet to learn.
They gravitates towards MPG the same way they gravitate to picture books, rather than one full of words. Because they cannot yet decipher the language.
But English is a powerful tool, although unnatural and clumsy in some ways (can't express emotions well, can't draw a picture). And I believe WIMP is similarly powerful.