To put it bluntly, it's about using future generations to tie Zhou Chun down, so that in the future, after all his relatives and elders pass away, he won't disregard the family!
Su Yuzhen had a similar idea, but she genuinely wanted to give birth to a child or two for Zhou Chun, so she wouldn't have any regrets in this life.
Zhou Chun was actually aware of all this, but it was difficult to say it out loud.
Of course, he wasn't firmly against leaving no descendants either.
Therefore, when faced with persuasion from his three closest people, he couldn't outright refuse and could only temporarily delay it by saying that his Essence Energy hadn't fully recovered, giving himself more time to think about it.
