Despite all of the lofty titles and vivid insults thrown around by children, parents are people just like us, which means they have illogical habits. Oftentimes, it's not until we're older and out of our parent's house that we realize just how weird some of their behaviors.
However, in some cases a parent's illogical quirk is so noticeable a kid can clock before they've left the next.
My dad, sister, and little brother put trash in the sink along with the dirty dishes. Makes me rage every time.
My mom spent over 4 grand on living room furniture (couch, love seat, two leather recliners) and she will not allow ANYONE, even her own children and grandchildren to sit on them. Whenever I'd invite people over everyone awkwardly stands around or sits on the floor. -__-