That's a large part of it, carrying on the blood line is super important to most East Asian cultures. The other part of the equation is that their cultural ideas leave no place for queer people in their idea of modern society.

It's kinda strange, but pre-western influenced East Asia was arguably less conservative in a lot of ways when it came to sexual orientation. There were more gray places in society for nontraditional relationships like court eunuchs, harams, and other noble positions that diverged from today's cultural norms.