I'm not sure if it's attributable to porn though. I think it's rather our individualistic, bordering on narcissistic, culture that is driving this.
As the old saying goes, it takes a village to raise a child. The next best thing after the village is the family.
But in a society where the individual is celebrated and divorce is so common, the whole burden of raising the child rests either on the mother or the father. And that is just too much to deal with.
I think if you look back in human history it was natural that the tribe would take care of all the children, thereby spreading the burden a lot. But we don't have the tribe anymore. And the families are now breaking apart, too.
[1] https://www.cdc.gov/nchs/nvss/marriage-divorce.htm?CDC_AA_re..., for rates since 1990.
I'm a DINK myself; I've watched the complexity of my friend's divorce with children and I perceive it as more evidence I've made a good decision.
They (conservative ones) seem to want to force births (against abortion & in some extreme cases, even contraception). But the followup on supporting kids is, like you said, not there.
* (political) do politicians want to and policies support having kids? Like helping with healthcare when needed or should you spend 10k$ for simple things per kid?