The distinguished adventure photographer Galen Rowell wrote an essay about this; he called it "The Hello Factor," published in "Galen Rowell's Vision," still the best book I've read on photography. Basically, Rowell's point was that our joy in interacting with other humans is inversely proportional to our density. On a remote peak, we'll gladly stop and chat with a complete stranger, because we're the only ones around. On a crowded yak-route road loop in a city famous for cycling, we won't even nod, because it's just another cyclist. Sad, but true.