PDAs of a different sort

Before you had kids, you probably had a policy about Public Displays of Affection between you and your significant other. And I bet he knew where the line was, too.
But when it comes to babies, all our rules go flying out the window. We coo, snuggle, kissy-face and baby talk in public without thinking one bit about the impression we're making on others. Why is that?
Is there something about kids that makes even normally nondemonstrative people give hugs freely? Is there something about babies that makes even the best grammarians lose years of education? And here's the biggie: is it cute or just stomach-curdling to see a normally rational adult go ga-ga over a newborn?
For the record, I'm guilty big time of allowing PDAs with my kid that my husband would never get away with. He gets hugs and kisses on demand, although at 5 he's making fewer demands every day. He's allowed to crawl in my lap, or hang on my shoulder, or wrap his arms around me wherever we are. But I never used baby talk, and at four he was using words like "mistaken" properly. But that's another blog.
--Misty