Hmm when I was a kid kid I was only playing on my TV in the living room during the day with natural ambient light :)
Anyway I've never been burned burned by tv or monitor lighting, but I've started to see less well in the dark just a few years after switching to lcds. Being under 30, maybe closer to 25 than 30. To the point that my wife asks me why I keep turning lights on at dusk in rooms where she sees perfectly with what's left of the sunlight.
It’s still not the same as a black screen that’s not emitting light.
You said it yourself actually: lcd monitors do require ambient light to not be painful. CRTs could do without.