Lots of my son's (14) school friends spend all day on their xboxplaystationwii or looking at porn on the net and have no idea of what goes on in the real world..
The real world? You mean like in the movies?
Perhaps the person you were talking to was not particularly interested in film and as such haven't heard of those people.
I come across many very educated and knowledgeable people everyday who have not heard of musicians, artists, writers etc who I think are well known. You know about what you come across and if you aren't that interested in film or tv then you won't know much about older actors (or new ones for that matter).
Not really to do with age.