She doesn't explain because because this model really is so obviously erroneous, but only after you accumulate enough experiences in life, or, if you want a shortcut, after you read enough books written by those who have experienced a thing or two. Some things can't be explained in a few sentences, because they are not mathematically true, but happen to be true in this particular world of ours. Sometimes, it's hard to explain how the world really works; you have to experience it in the flesh, and it takes a while.