High pitched voice

Why do some women feel the need to speak in an extra high pitched voice when talking to children and retards? At the moment in the park across the road from my house, a bunch of special people and their helpers are having a Christmas picnic. I can hear the shrill voice of one of the helpers calling out the names of each attendee to collect their Christmas present. All of the picnickers are all fully grown adults! Do mentally disabled adults need to be spoken to in that concending tone? I hated it when people spoke in that squeaky tone to me when I was a kid. I thought, "Hey, dude, I have ears and I understand English, there is no need to speak to me like I'm a deaf baby."