I could, and there are many 15 minute intervals in my day where I don't have to do something - but not so many that I don't treasure them. Meditation isn't the same as relaxation when you start off, as I understand it - it takes some concentration and effort, and my reserves of both are usually running pretty empty all day.

Like others have said, I'd rather have an extra 15 minutes of sleep, or an extra 15 minutes in the shower, or 15 minutes to just sit and eat breakfast.