Why Don't Babies Talk Like Adults? (scientificamerican.com)

"This E*Trade commercial is only the latest proof of what comedians and movie directors have known for years: few things are as funny as a baby who talks like an adult ..."

Well, let's not carried away. It's cute in small dosages.

EDIT: Just came across this:

     Get the Rest of the Article  

with a link to pay to read the full article.

Because they're stupid babies.

"Why don't adults talk like babies?" would be a more insightful question in my opinion.

So, uh, practice makes perfect, and babies just haven't been around in the world long enough?

My experience raising two children is that adults often talk to babies with babytalk. we talked to our babies with adult language and they didn't really use babytalk.

Market segmentation.