"We live in an incredibly language rich enviroment"
Baby's and children live in the environment created by their parents. If there is little interaction, then the child often grows up in an environment rich with nothing.
We mix with other family's who share the same values as us, so many on MN may not come across parents who are silent with their baby and each other.
One of the courses that i run for parents is Webster Stratton, which teaches why a "running commentary" works well for children, it combines other factors.
I met a little girl who barely spoke but communicate partly through makaton, which she had picked up from "Something Special", her brothers did not speak, within two months of being in Foster Care, they were as verbal as you would expect, in a child without SN.
Children can often appear as having disabilities when SS first get involved, it then proves to be purely environmental
It is dis-pairing that many on MN seem to want to deny that there are children being damaged by a deliberate lack of care.
I think that technology is now having an effect on males, in particular.