The short answer is I don't have those parents. They consider themselves to have more important things to do, I guess.

When I lived with my parents and my dad was in the living room while I was playing something, I'd always get really nervous. He'd put down his paper or book or whatever and silently watch with a somewhat judgemental face. He'd sit like that for 5-10 minutes, and all the while I'd know what was coming: some smartass sarcastic comment like "why are you harrassing that bug?" (drawing Cure from a Caterchipillar in FF8), which he'd know I couldn't really give a meaningful answer to. As a result of him continuously doing so, whenever he started watching I'd feel pressured to do something that seemed worthwhile as if to prove that it was a "valid" form of entertainment. Oh, the hardships of parental judgement.