I can see the ease of use argument, and that Apple products certainly do well at that. But, thinking on a longer time line, isn't that target audience shrinking. What is the life expectancy of the pre-computer literate population? How big is this audience now? I'm just asking. I have no idea.
On the other hand, a much larger audience would be the vast unwashed masses in the third world who use cell phones to access the internet. The sales volumes are higher, while the price point is lower... I wonder if Apple would go there, or would they leave that market to others.