Because some people are so incredibly delusional, I mean they must be in order to see it as being an acceptable and justifiable thing to bring life here, I think that a lot of them are driven by extreme selfishness as well, if one was really a caring person then they wouldn't create unnecessary suffering by bringing life here.
I think that to procreate is such an incredibly cruel thing to do, nobody who is not yet existing deserves to be burdened with something so hellish and futile as having the ability to exist in this harmful world that is filled with risks and the potential to suffer so extremely. The non existent should just be left alone in peace, it's tragic how people continue to bring life here.