It is "birth control" but in sort of opposite way. People are now much better informed, thanks to internet and devices like iphone. They do not have to relly on state education (that wants more babies) and popular shows like Friends.
State founded school is not going to tell you it costs $1200000 to raise baby, or you have 50% chance it will be taken away.
It will also push stats made in lab controlled conditions, and gloss over unreliability of such medications in real life (like if you would skip a pill for a few days).
Failure rate of birth control in normal life is around 10% per year (if you drink, forget to take pill at very exact time, use antibiotics). So there would be about chance 50% to get unwanted baby over years. Well informed person will not make such mistake.
Edit: about the cost
I said the "cost is", not that they are "spending it". There is lost opportunity, lost salary, lost investments, inflation...
It is not 18, more like 24 years.
Let's do some some math, take $600 rent over 18 years = $129,600. With 5% annual rent increase $202k. If you would reinvest that rental income with 5% yearly return $304k!!!
Stay at home mum for 5 years, at $60k = $300k. If you invest that into retirement account when baby would go to school, for 12 years at 5% yearly return it is $538k