I Hate Watching My Smart, Articulate Friends Transform Into "Mommy" and "Daddy"

Care and Feeding is Slate's parenting advice column. Have a question for Care and Feeding? Submit it here or post it in the Slate Parenting Facebook group. I don't have kids but a number of my peers now have babies and toddlers, which means I've heard an awful lot of my smart, articulate friends talking about themselves in the third person, like Elmo. I understand why toddlers do this in their language acquisition journey (pronouns are hard!), but why on earth do my friends say, "Mommy loves you," and, "Mommy needs you to not touch that," when they are "Mommy"? Basically, is too much time with a toddler scrambling their brains and I'm within my rights to roll my eyes, or is there a real cognitive reason why my friends speak this way to their kids?