With swaddling you recreate the pleasant, warm environment from the womb, which has a calming effect on your baby. It reduces anxiety and improves sleep.
If your child is restless or cries a lot, swaddling is an aid to get your baby relaxed and calm again more quickly. In addition, babies are not aware that they have arms. As a result, they often move themselves awake, because of the swaddling they cannot move their arms which again calms them down.