Many baby stuff need 5 min in boiling water for the first time. i am wondering the exact reason, why not just pasteurization enough?

Context matters: These products are sold worldwide and end up in settings where creek water or unsanitized well water is used in food preparation. I would NEVER expect a mom to do this living in the normal community in the US where water supplies are safe. These should be treated like your regular dishes & utensils, with simple cleaning prior to and between uses.