It is important for a good healthy attractive body.
Most people have routines and specific favorite workouts or activities that blast calories away or tone muscle. It is usually against most peoples nature to vary in their routines to much. Although, it is suggested in recent studies that it might be good for your metabolism.
Apparently your body is just designed to get use to things. If you eat a routine diet (and are trying to lose weight) your body will adjust and you may plateau. Its suggested that this can happen with most work out routines also. Which was specifically why p90x was created actually.
I personally have restless life syndrome, I have trouble developing ANY routine ever. In fact my mind seems to reject routines so much so I won't wake up the same time, get sleepy the same time, or do ANYTHING the same way twice.
(with of coarse the exception to a few minor anal tendencies, like making my pbj)
So, I think though I have an edge on most folks by switching my workouts up constantly, I do feel that it is heathier to have developed a basic routine or pattern in life. Life is always about balance. A healthy balance is actually the answer to most questions in life.
So while most need to work on "switching it up", I need to reel in my ADD and spontaneity and try to carve out myself some healthy daily and weekly rituals.
Every man has their quest. :)