I have always called my parents Mommy and Daddy. Those are their names! They aren't (weren't in Daddy's case) Mom, Ma, Dad, Father, or (god forbid) Charles and Barbara.
I'm not sure if this is true of other adults, particularly boys (though I've heard Howard Stern call his mother Mommy on air). It might be a sign of childishness, denial about age, or whatever. But in my family (this is also true of my sister), our parents are Mommy and Daddy, forever and always.