Many parents wonder why baby onesies have lap shoulders and assume that it’s to make it easier to get over their head. This is actually not true. The reason for the envelope-style shoulders is to make it possible to pull it down off your baby’s body. This can be a real lifesaver when your baby has a poop explosion. You don’t want to have to take a poop-covered onesie and pull it up over your child’s head, risking covering them in it. The wide neck and lapped shoulders make it possible to stretch over your baby’s shoulders and be pulled down off your baby.