I know baby talk has a function. Especially in infants. And without perusing your link yet, @thisismyusername, it’s useful for infants. Seek shared a TED talk on FB about how babies acquire language. By about 6 months they can recognize, and respond to, things said in their language, involving their language cadence, sound, pronunciation and tonality. We impart all of those basics with baby talk.
However, we are friends with my daughter’s friend and we sometimes babysit her kids for her. The mom is all worried because her son isn’t talking much yet and he’s almost 3. However, she also talks a lot of baby talk to him, and yesterday I couldn’t help but notice that when she was giving instructions to him to do something, she spoke really loudly, like he was deaf! I was like…what? Why are you doing that? Just talk conversationally to him! I didn’t say anything, of course. But it’s kind of the same thing some people do to old people, even if they don’t know them. Speak loudly on the assumption that…IDK. They’re deaf. Or stupid. IDK.
I just wonder why some people do that.