There is always another option to get a workout in no matter how busy your life is. Are you dragging the kids to and from soccer practice? Why not get in your own walk or run while they are busy at practice. Do you love reading? Try downloading some audio books and going on a walk while listening to your favorite book.
Using a treadmill can be the way to go for those who want to improve their aerobic fitness while being able to stay in the same room safely at home and not out jogging or running on a sidewalk somewhere. The treadmill gives one an always available always ready to use option for maintaining fitness.