It's a chicken or egg issue.

People capable of walking the most steps will be healthier than people not capable of walking the most steps. Those healthier people are likely to live longer. You can't say that the people are living longer because they are taking more steps.

I've heard this taken to the point of extreme ridiculousness:

One study said that men who are sexually active in their 80's are less than half as likely to die of a heart attack than men who are not sexually active in their 80's.

No kidding! A man in his 80's who is still sexually active has to be in pretty fantastic shape.

Well I do 15,000+ steps a day, including power walking and jogging. An off day is 10,000 to 12,000. Under that I feel guilty. People should get off their butts and walk more, instead of driving those gas guzzling SUVs -- stupid unnecessary vehicles for inclinded minded people. I hear people say, 'oh just walk for 5 minutes every day, that's all you need." That won't do diddley for your health.