I remember listening to an NPR show where a doctor talked a lot about this, and how all of the shaming of co-sleeping might contribute. She claimed a non-obese, non intoxicated parent sleeping with the child on a bed isn't all that dangerous. That same situation on a couch is deadly. But the messaging is more abstinence than harm reduction, so all many people hear is "co-sleeping is dangerous"

Consequently, exhausted parents accidentally fall asleep on the couch holding their babies when they would have been better off just lying down and napping.