Why hasn't millet become the same staple food as rice?

To say that the difference between north and south is mainly rice or pasta, wheat accounts for a large proportion in the diet of north and south people. The traditional food crops in China are sown in spring and harvested in autumn. There is a cloud in ancient poetry, a millet is planted in spring and ten thousand kinds are harvested in autumn, which is called millet. However, millet sown in spring can't get food until autumn. What do people eat in summer? In this way, every summer, there are often crops that are green and yellow, leading to a food crisis, and then there is wheat. As for wheat, sowing in late autumn in the north and maturing in summer after winter and spring will not hinder the sowing date of millet, but also become people's rations when the green and yellow crops are not harvested. In this way, the emergence of wheat has solved people's food crisis, and wheat has also been widely concerned and planted. In China, where food is the most important thing for people, wheat has gradually become an indispensable physical object in people's lives. Oh, Xiaomi is ignored. Well, Xiaomi's C position was robbed. In addition, another reason why millet can't be used as a staple food is the result of official promotion at that time.