As I have written before, I don't always have the time or money to attend a yoga class. And since I run, ride my bike and swim, I often use yoga as a before or after complement and companion to my other exercise. In those cases, it's great to have some ready-to-go videos, especially if you are time crunched.
And on those days that I haven't gotten to do any of my other activities, it's great to clear the mind and stretch the body and think to myself, "Well, at least I got 15 minutes of movement in." Because one of the only ways to keep exercising is to make it a habit, and make it easy.