16. "That answer is used for really complicated questions too" In response to In response to 14
Like stuff relating to interpersonal relationships (love, sex, friendship, office politics, etc).
I think you need a little bit of experience and maturity to understand things like that so "You'll understand when you're an adult" is sometimes appropriate.
Why are mom and dad always arguing? Why don't cousin's dad and mom get married? Why don't we hang out with grandma?