From what I recall, they tried including housework and other normal activities in the 30 minutes and most americans
still couldn't reach goal
Plus, that 30 minute recommendation is generally for people at a normal weight that have never been overweight, who are just trying to do the minimum amount to stay healthy and try to ward off illness. Once you take weight loss and maintenance into consideration, we need a minimum of 60 to 90 minutes most days of the week