They do that because the most common transmission in children is from the mother. Because parents lie about drug use and sexual behavior.
Even if the mother is tested clean in the hospital it doesn’t mean she won’t become infected after they leave the hospital either through her own behavior or by a partner and then transmit it to her child where it may spend the next 50 years silently destroying their liver.
Not worth mandating to everyone.
They aren’t actually mandated. You can still refuse any and all vaccinations for your children.
The CDC guidelined are mere suggestions.
I actually refused the HepB for my firstborn as the shot was new at that the time.