People with kids or babies always want them to eat natural foods with no preservation, even if are a bit more expensive than the other available options. What they care about is the quality and health of the kids. So keeping this point in head, most of the brands uses the technique to compete with the other in-market brands. And that's what the shopkeeper did in this case.
Mike should have read the listed ingredients on the baby food jar. I think both of them would have the same, except a few.