I think it's about shifting the bell curve of the population's exercise.
Those who currently do 5 000 steps are encouraged to do 8 000.
Those who currently do 8 000 push harder to achieve 10 000
Friend has discovered that she easily achieves her 12 000 during the week, but is remarkably sedentary at the weekends. Now pushes herself and routinely achieves 12 000 daily.
And remember, cardiovascular fitness (achieved through moderate to vigorous exertion) is different from having an active lifestyle (10 000 steps a reasonable example). Both are good for your 1) longevity and 2) shortening the period of poor health at the end of your life.