Babies can get HepB from being born, it's pretty messy, fluids of all types get everywhere, including in the baby's eyes. That's why the WHO recommends a "birth dose" if it's possible the mother is infected. You get another two doses separated by six months after that for more durable and improved protection, so you don't have to start the whole three dose 1.5 year long series again when you want to have sex or become a medical worker or whatever. Otherwise, I totally agree with your points on smallpox, you really should be able to get vaccinated if you want to.