I don't think there's anything uniquely beneficial about walking in comparison to other types of aerobic activity (running, biking, playing a sport) - though it

I don't think there's anything uniquely beneficial about walking in comparison to other types of aerobic activity (running, biking, playing a sport) - though it may be more accessible/enjoyable which is important when considering adherence. It makes sense that mortality risk would be reduced by increasing step count, as that means increasing aerobic activity. See the 2019 Physical Activity Guidelines for Americans: https://health.gov/sites/default/files/2019-09/Physical_Activity_Guidelines_2nd_edition.pdf https://health.gov/sites/default/files/2019-09/Physical_Acti... Page 35 specifically outlines their justification for the recommendation of 150-300 minutes of moderate physical activity per week for adults. I will add that something like 80-90% of Americans don't meet the physical activity guidelines (150-300min moderate intensity aerobics + 2 days of muscle strengthening activities for major muscle groups, per week) - walking is one of the most accessible activities and is fairly "easy", so I think this is useful as a blanket recommendation.