During the Han dynasty, why were merchants considered such a low class in the social structure?

During the Han dynasty, merchants were considered such a low class in the social structure because they were usually very poor and they lacked education. The Han dynasty valued those people who had proper education and showed decorum, and who had money and were considered to be good-standing. Merchants didn't fall under any of those categories, which is why they weren't really valued during this dynasty's rule.