It's just not used to it.
Is it enough to be unaccustomed? In those days, that was enough. The famous "Seven Out of the Rules", the first of which is "disobedience to parents". What is "disobedient parents"? As long as your parents (in this case, your husband's parents, that is, the woman's in-laws) don't like you, you are "not good"!
Why does Lu Mu not look at her daughter-in-law? Some people say that they are worried that their son is indulging in love and delaying his future, some people say that Tang Wan is childless, and some people say that Tang Wanli is not careful and her mother is not careful. It all seems to make sense. But if you think about it, none of these "truths" can be a reason to divorce a wife, but at most an excuse.
Lu You married Tang Wan at the age of nineteen. Neither early love nor extramarital affair. Couples and beauty after marriage, which will become a resistance to the "future"?
The ancients did attach importance to "no filial piety has three, and no queen is greater." However, if the wife is infertile, she can take a concubine, which is a very common practice. Moreover, if she divorced soon after marriage, how could we conclude that Tang Wan was infertile?
As for the "number of etiquette is not weekly", it is even more nonsense. Tang Wan is Lu You's cousin and the daughter of Lu You's uncle. Lu Mu was Tang Wan's aunt. Aunts and nephews should come and go frequently and know the roots. If Tang Wan was really a rude and rude person, how could Lu Mu know nothing? How could a son marry such a woman? If Tang Wan is gentle and courteous, even if she is just a normal person, how can her temperament change drastically after marriage and be "rude" and "imprudent" to her aunt and mother-in-law?
The contradiction between mother-in-law and daughter-in-law has been common since ancient times. From the perspective of modern psychology, in the words of Zhang Ailing's Heart Sutra, "they are just two women who love the same man", there is natural competition and competition.
In "Peacock Flying Southeast", Jiao's mother was not accustomed to her daughter-in-law and forced her son to divorce his wife; Lu You's mother could not get used to her daughter-in-law and forced her son to divorce his wife; Empress Dowager Cixi was not accustomed to the Empress Alute of Tongzhi, nor was she accustomed to Guangxu's concubine Zhenfei, but she did not force her son to divorce his wife, but personally tortured both daughters-in-law to death.
They don't have a good reason. Nor do they need a good reason. "Unaccustomed" is the fullest reason.