Do you consider yourself these people's friend?
If you're completely disinterested in their milestones, that sounds more like an acquaintance.
But to your question, yes. I actually care about these things for acquaintances and random people too. There are limits to how much I care but it's not zero.
I'm sure that a few, very dedicated, women are doing this.
It's unlikely to be widespread. Sex is one of the most powerful drives humans have. We generally have a terrible track record of trying to convince people to avoid or even delay sex. Even when people believe that their eternal soul is on the line they keep having sex. That's exactly why all the "abstinence only" policies fails so spectacularly.
There are cases where voluntarily giving up something important has led to change. Hunger strikes are the prime example of this. They can have the affect of drawing attention to a matter and raising sympathy.