Why does my Boyfriend talk to my little puppy in Baby Talk?

I have a mini yorkie that's about 2 years old. She is only about 1.7 lbbs and 7 feet long, and maybe 5 inches tall. Whenever my boyfriend comes over he talks to her in babytalk. He says things like. o0o0o0o0o The little baby.. And when he gives her food he will say o0o0o0o little yum yums. And then when he pulls the treats out before he gives them to her he will say o0o0o0ohhhhhhh in this little baby tone of voice.. My dog likes it i guess becoz she wags her tail alot when he starts talking to her like that but why does he do it? I want to ask him but is that normal? should I just leave it alone?