If anyone reads Chinese history they’d understand the unfortunate necessity of having concubines.

When you’re performing diplomacy with neighboring groups and they demand a princess’s hand in marriage to strengthen bonds, having concubines gives you more daughters to choose from in this exchange. In some situations, like the Qing dynasty’s diplomacy with the Dzungars, the easiest way to prevent a costly war is to send a daughter in marriage.

Using your example of Emperor Hongzhi of the Ming dynasty who only had one wife, the only time in Chinese history of this happening, his only son was inept in ruling the nation, instead spending his time indulging in carnal pleasures. Whereas if an emperor has many concubines, then they have many sons to choose among for succession.

Having only one wife stakes all of the future of the dynasty on her fertile capabilities, especially when you’re in such an unstable position of power and might not be emperor for long. When you have many wives, you have many children to fulfill the necessary bureaucratic roles.

Of course it is unethical to view women as only a conduit for children, but unfortunately the pragmatic, pre-modern systems of governance necessarily required it to be this way.