Not only has the population increased by more than 100 million people since 1981, but the number of pedestrians has increased even faster than the number of people has, with ever more people going carless - especially in some of the largest and most densely packed cities, like NYC.
That these values are staying so low seems to be the real story, as it would seem to indicate that cities are doing a great job of adjusting to an increasing pedestrian population. But, if it bleeds - it leads, I suppose. Perhaps with the modern addendum that if it doesn't bleed, then just splash some ketchup on it.