There are many reasons of course, but one big reason is obviously education. In the Meiji period, Japanese educator structured Japanese English education in such a way that people would not speak English! We still live on that tradition.
Another big reason comes from economic theory; I mean, economics sheds light on it, more accurately put. Nobody really wants to learn English. As many of you know, economic algorithm is based upon two parameters; supply and demand. They lead to equilibrium by way of invisible hands. So the situation is that demand is so low that it is below equilibrium situation. Simply stated, if people really want to learn English, they will do so no matter what. Do not call it a tautology; it is not. Why not? That is a difficult issue. I can explain it to you upon request.