Cardio isn't the best way to lose weight in any case. Lean muscle building is far more beneficial. Adding lean muscle and doing high intensity short workouts are shown to boost your resting metabolic rate far better than cardio, and boosting the resting matabolic rate is mucho bueno for weight loss.
Essentially, unless you're training to become a marathon runner or some other thing that requires excellent cardio, it's not that useful. Yes, you will lose some weight doing nothing but cardio, but eventually your resting metabolic rate keeps slowing down and you see very diminished results.