Knowing your baby can't be done by reading books or hearing what other people think of how to parent. Knowing your baby means spending time with your baby and believing s/he is an individual. All parents need to do this.
In many ways, sleep is a social activity and is hugely important to our social well-being. Though we sleep alone in our society, this is not how we have evolved, and we see this when we return to shared sleep when we marry or live with another person.