Besides slapping God in the face (artificial contraception is like binging and purging, except this is "binging and purging" with the greatest human power, the ability to co-create children with God), the implications for society are obvious.
If there is a God, that slap to the face is between them and Him.
the implications for society are obvious
A statistically insignificant percentage of people choosing not to have children really makes no difference to society at large. Furthermore, I would wager that DINK couples contribute more to society than they take out, financially-speaking.
In any event, the only reason we are particularly concerned with birthrates is because we have set up the social security pyramid scheme. If it wasn't for that, all we would really need is a replacement level birthrate, and we are close to that right now. We can make up the difference with (smart) immigration, if need be.
And God told you this directly? You have an insight into The Almighty's thoughts and desires? He came down to you and expressed His Divine Displeasure about somehow forcing those who do not feel the self-centered urge to make a half-harted stab at some sort of immortality?
Insolent, Self-Rightous, Blasphemous and Sanctimonious!