It's so tempting to want to get our workouts done in the shortest amount of time, but sometimes you can get better results with lower intensity, longer duration. Walking seems to fall in this category for me. It's all about the desired result. Inweight lifting I like to go for low weight, high repitition. I see walking as the cardio equivalent of that. Sometimes it's good to sweat like crazy, but other times you need to be slow and patient with your workout. I'd love to get comments on this!
I've done some of those intense cardio workouts (like super intense flow yoga meant to make you sweat) and I don't think it really does much in the long run other than mayyybe burning a few more calories in a session. For older people and those with physical limitations, intense cardio is not only unnecessary but possibly counter-indicated. Also, how many times have we heard of young top athletes collapsing due to a heart attack? I don't think our bodies were necessarily meant for a lot of intense cardio except for the short sprint away from danger.