No best answer

Because the processing and manufacturing of molds are relatively difficult and the cost is relatively high. For example, a mold master needs several years of training from a novice to a veteran. In addition, the structure of the mold and the accuracy of the mechanical equipment also determine the cost of the mold, so it is relatively expensive. But in fact, for real mass production, the cost of molds is not a big deal, so molds are needed to reduce costs.