Are we now pretending that every stranger in the world matters to us just as much as our own children? Don't make me laugh.
No, of course not. Just that if a very low-risk vaccination for my children, as part of the usual schedule, raises herd immunity and reduces a really devastating risk for pregnant women, then why the hell not do it? The fewer children who catch rubella, the lower the risk of a pregnant woman for whom the vaccination has not worked, or for whom it is for some reason unsafe, catching rubella and having a child with CRS.
The nearest parallel I can think of is giving blood. You know, when they shove the needle into your arm, that you are taking a very small risk of something going wrong. But, like thousands of other people, I go ahead and let them do it anyway. I also hassle my DC to become donors. Why? Because
a) My DM lived the last few years of her life dependent on other people's donations: as a result of their actions, I had her for a few extra years and I hope that as the result of my boring O+, I can help to buy some extra years for someone else
b) I, or DH, or one of the DC, or someone else I care for might one day need to receive blood, and we can hardly rock up and expect to get it unless someone donates it
Don't get me wrong: I can be as selfish, ill-tempered and judgemental as anyone else. But I donate blood, and persuaded DD to become a donor, because for me the risk is hugely outweighed by the benefits to society.