I'm not sure I follow? There are plenty of fascinating things to see or do within an hour's drive of London - it's not like cars go faster in the US, and if anything there's more variety in a small area in dense England.
Getting out of London into proper countryside does take some time. One of the things I missed when I moved to London from Manchester was being able to take a train to the edge of town and walk out into the Peak District. Now that I live in San Francisco I can easily drive out somewhere nice, but still miss being able to take the train and enjoy a couple of pints at the end of my hike!
I think they are talking about beautiful natural places where you can spend sometimes alone. It's my biased interpretation, living in London I don't care about musicals, museums (just because they are always full of people) or anything with concrete in it or crowded, I just want a beautiful place where I can spend some time alone.