Fuck both of those. Seriously, I cannot stand the elders = respect thing (esp when they're TERRIBLE people), and people who usually say "you'll understand when you're older" is their lazy excuse to not tell someone younger.
Y'know what happens when you tell a kid/teenager "you'll understand when you're older"? They obsess about it and since the Internet is so fucking accessible nowadays, they will likely be misinformed or delve too deep than had you just told them to begin with.
But yeah, pretty much every one of these mentalities/sayings is just the worst of societal "norms" that came from ages ago and continued through generations because tradition.