They're just different, each with different innate abilities. People are better at language, the arts and emotions that make life worthwhile. Technology is better at such things as logic and mathematics, both invented artifices. Norman's presentation is eminently accessible, with incidental insights into such matters as primitive office procedures, and why, for addition and subtraction, Roman numeration is superior to Arabic. As he notes, books are one form of technology.
Television is another.
Lots of things make us smart, Norman points out.