There's already 7,6 billion of us, tendency rising, I see no good reason why I should contribute to that number growing even faster because it seems already unsustainable enough as it is.

In that context, I see especially no reason to have any biologically related offspring. It's not like there's a shortage of orphans, because adoption might just as well be another option to actualize this inherent need to "leave something lasting behind as to give purpose to our existence", by passing on values and life-lessons.

Too bad the barrier of entry to that is usually very high, I guess for good reasons.