Here are some great reasons to do cardio:

To lose fat and look better! – want 6-pack abs? Only way is to lose fat thru cardio and proper nutrition.
Cardio can improve your mood and significantly reduce depression. Its been proven by study after study, cardio can make you happier!
Perform better at school or work! Daily cardio reduces mental fatigue and gives you more energy. A recent study from the U of G showed that daily cardio reduces fatigue by 65%
To live a longer, healthier life.
To help gain muscle.
Cardiovascular exercise should not be boring, if it is then you are doing something wrong! There are many types of cardio, its not just traditional jogging! You can do interval training if you find jogging boring. You can find a team sport you love and do it with a friend or spouse and the time will fly by. If you are stuck indoors on a machine, then find a good book, listen to the radio, or watch TV – find a way to make it interesting and enjoyable.If you don’t have much time then jog to the gym, walk you kids to school, walk your dog, or start using your bike for transportation.