The ability to read is not part of our evolutionary heritage.

The human brain has existed for roughly 60,000 years.

The alphabetic code has existed for only 5,000 years.  

Language acquisition and use are innate, whereas reading skills are not.

To be able to read, the brain has to recruit resources from quite disparate parts of the brain that have likely evolved to perform quite unique functions.

Evolutionarily, we are not designed to be readers (Goswami, 2008).