Less unwanted pregnancies which result in less abortions, single mothers relying on taxpayer social safety nets, or extra state money spent on kids falling through the cracks of the foster care system.
I se how less sex is an easy solution to the problem, but it is also the wrong one. Your teenage years are when you have the more energy and hormones, you are basically built to have sex. Not to mention it's healthy for the mind and body.
It would be like not allowing teens ride bikes because of possible crash with cars since stats show teens are more likely to have accidents than adults.
Better find a way to limit the accidents themself: you get healthy kids, having fun, and they grow into better adults.
This is likely a case where the evolution of human culture hasn’t caught up with the available medical technology.