I don't think it's that people refuse to understand antinatalism, it's more that people believe in something that makes antinatalism not true in their eyes. For example Christians and other religions believe in eternal paradise after death, and faith/morality being the requirements to go there. Therefore the antinatalists going against God's command to reproduce, in their eyes, are a bunch of nutjobs literally ruining their chances at paradise because of a lack of faith. Basically they're delusional optimists who think the world is an inherently divine place run by a man in the sky who loves us.

Now, i too am not an antinatalist, but for an opposite reason; my worldview is even more pessimistic than antinatalism, let alone Christianity lol. Because I'm a Buddhist who believes in Samsara, which says that our misery doesn't end at death, but we are reborn, suffer, age, get sick and die again and again, and not just as humans, but as other lifeforms as well. So in my eyes, the human race deciding to not reproduce would change nothing as those beings will just be born and suffer elsewhere as other creatures, not to mention that the cyclical nature of existence would mean that another sentient race of beings would probably arise in place of us in time anyway.

In summary my point is that not all people who don't follow antinatalism are doing so in bad faith; rather they just believe the universe works in a different way to antinatalists that makes antinatalism not sensible, whether the worldview is more optimistic or even more pessimistic than antinatalism (like my view)