They cry much less and they grow to become happier, more intelligent, more independent, more loving and more social than babies who spend much of their infancy in infant seats, swings, cribs, and all the other plastic baby-holding gadgets that don't provide babies with human contact. Many new parents buy a sling or receive one as a gift and end up not using it because they can't figure out how to get themselves and the baby comfortable. In other cultures, parents naturally know how to use slings, because as children they grew up seeing slings used, and wearing their siblings in slings. Since slings are new to our culture, anyone just being introduced to using a sling will usually need someone to show them how to get themselves and the baby comfortable. Parents are thrilled when they learn how comfortable and convenient it can be to meet their baby's needs and still do all the other things they need to do.
Slings are different than front carriers.
A sling is like a hammock. From newborn to the sitting-up stage, babies' spines are best supported in slings because their weight is distributed along the length of the spine. Front carriers that hold the infant upright with their legs hanging down, can stress the spine because they put all the baby's weight at the base of the spine. There are many styles and brands of slings. It is helpful to try several and have someone who is comfortable using each one show you how to use it.