Actually, to be fair, whether it's Lady Liang or Zhou Xueli, they all know that Wu Lihong is a golden opportunity with extremely high value, especially since Madam Zhou gave birth to a daughter before even going through the traditional betrothal process. This leverage is not insignificant; after all, Wufu is also part of the Wu family's bloodline.
But bearing a daughter out of wedlock does tarnish one's reputation. Now that the other party is willing to take them as a secondary family, it's a sort of resolution. The Zhou family neither has the capability nor the ability to dictate or demand more.
If Madam Zhou and her daughter were living as they once did, the Zhou family would not say anything. But now, the mother and daughter live comfortably, probably even more indulgently than some Official's Family's Madams. Truly wanting to acknowledge their roots is likely not worth the loss!