[Valpal1]

Because they were commanded by God to teach the Torah to their children and to write scripture on their doors and gates.

Their religious and cultural traditions are based on a high level of literacy and the study of Torah is considered the highest form of worship.

[Cronos]

1. Teaching the Torah does not mean "reading" -- many ancient peoples retained their histories orally. Think of the Homeric epics or the Mahabharatha and Ramayana etc.

2. To write teh scripture on their doors and gates -- illiterate Jews in Europe got their rabbis to do things like this. It would have been the same in BC times.

Being literate, investing the time and effort to do so was not worth it for most people before the invention of the Gutenburg press and paper made from wood pulp

Before that books were just too expensive, too rare for most to have. Even the Pentateuch would be restricted to a few copies -- remember that it was "lost" during the period of Kings and found again during Josiah's time. What do you think the Israelites were doing during that time? It was oral