If you are going to spend your valuable time doing something then it either needs to be fun or doing you good. The ideal is both where your activity is both fun and it is doing you good!
Let's look at the why exercise question first. The hard truth is that any exercise is good for you; it will immediately improve the quality of your life in a whole range of different ways. The most instant change is a better mood. After a stressful day at work a burst of exercise will definitely make a difference. Your body produces powerful chemicals during physical exercise called endorphins that are the 'feel good' hormones. These will boost your mood, if you're feeling down it may be that all you need is a 30 minute workout.
Exercise has also been proved to increase your confidence and self esteem. Regular exercise will significantly reduce the risk of a whole range of health related problems; blood pressure reduces and improves any cholesterol problem you may have. Your quality of sleep improves and you can even get a better sex life! A recent long term study showed that for people over 50 taking up exercise was a beneficial as giving up smoking.
Ok so that's why you need to exercise. Now let's look at the question why stomach exercises?
The most obvious answer is to look good, just imagine yourself with a slim tummy. Maybe even with a six pack too? You'd have to admit that it would be great to have a better looking middle. Even in the winter with baggy jumpers to hide your bulge! All of the media images portray the steriotype of slim stomachs as sexy and good looking and chubby tummies as a failure. I'm not saying I agree I'm just pointing out the commonly held view.
Actually the more important reason to take up stomach exercises is to help strengthen and protect your back. All of your physical movement is cantered around your middle. The solar plexus, just above the navel, is our centre of gravity and our pivot point. So with a stronger stomach our back can function better. We can have more fun with sports activities, even simple walking and running get easier too. The stronger your core strength is the easier you will move through life.
As we all get older back pain becomes a lot more common. It can really take the fun out of your life. So if you take the effort to strengthen and protect your back your life in years to come will be far better.