They have to give it to newborns, before the parents have a chance to notice the baby's "normal," so they don't notice when the baby goes downhill. If the baby never had it (eye contact day 1, calmness rather than fussiness, sleeping well, etc), then the parents are never the wiser that their child isn't living at his full potential.

For background, my children were born at home and vax free. People commented that they have never seen a newborn so aware and make eye contact. If all you've seen is hospital born babies with hospital protocol, you think that's what all newborns are like.