If your parents are not intellectuals then they don’t spend as much time trying to get you interested in ideas when you are a kid. So you are first exposed to them as an adult when you can appreciate the feeling of discovering ideas on your own. You are probably in college so you associate discovery with independence and counterculture.
If your parents are intellectuals they bore you to death as a kid with their lame ideas. By the time you are an adult and you can potentially appreciate them you are deprived of the chance to discover them for yourself. And anyway it all just reminds you of your parents.
Verifying this is our Thanksgiving Social Science project while surrounded by grandparents and their children and grandchildren. (Of course you can probably substitute “discovery of ideas” with just about anything and the logic is undisturbed. But on top of “Gardening is for losers because my loser Dad was always talking about his lame garden” there’s something extra having to do with the complementarity between the act of discovering the ideas and the ideas themselves.)