I have a theory. Swaddling and putting in crib of a newborn was recommended to accommodate getting parents back to work as quick as possible.
Discussion
Swaddling seems to have a calming effect and has been in use at least since the Middle Ages.
But the AAP made guideline to keep the babies on their backs when sleeping. Prior to that they were made to sleep prone.
I can’t speak to that one way or another. Only that swaddling has been around for a long time so it seems likely that it’s useful. I’m sure I heard somewhere that babies would be swaddled and that hung up in their swaddles. 🤷