Do They Call Their Children Adults?

"Can you hand me my calculator?"
"Sure thing baby."

You might think that this dialogue was between a regular person and an ultra-smart infant, one plotting to take over the world, or possibly do its taxes from the business it started; "Baby Buggy Bumpers" a rubber padding you can easily line your stairs with- but no, if you thought that you would be wrong.  Dead wrong.  Ok, you'd probably be alive, but you'd still be wrong.
This conversation is between two adult humans!  Ones that are either dating or married!  To each other!  I know, it was hard for me to believe at first, I thought the genius baby scenario was much more plausible.  Apparently though, calling your significant other "Baby" is a term of affection or endearment.  Why you would compare the person you are attracted to to a baby is beyond me.  It's sick, actually.  Who wants to make out with a baby?
"Hey babe."
Is that an implication of a toothless, fat faced incontinent?  I'm surprised there are so many successful relationships with that kind of name calling  going on.