As a childless adult, it's my duty to be part of other people's lives and support families by being a trusted adult (trusted by parents and kids) and be a good role model for others' kids.
Why? Because we live in a society. Today's kids are tomorrow's adults. There are, unfortunately, a lot of terrible social influences out there, and parents can't battle society alone. Young boys and girls need to learn and develop healthy relationships with men and women alike, beyond just their parents, in order to have something to model themselves after and to learn how to treat others with love and respect.
And this is especially so for singletons. A lot of the bad and warped ideas about "relationships" and even self-esteem comes from unhealthy views of romantic relationships. Ideas like if you're not good enough if you don't have a boyfriend/girlfriend. Or ideas that men and women cannot "only" be friends (objectification of other sex). Ideas that men are owed relationships and sex by women (incels). Ideas that it's better to be with a bad partner than to be single (abuse).
Parents can't fight all of that on their own.
If in doubt, you can check your immunity along your normal bloodwork. I asked my doc to check, it was just an extra requisition/vial.
I had to get the full dose (two shots, not just a booster of one) because I had no immunity, even though I had both shots as a child. Immunity can wane over decades.