The question is obvious as well as the answer and the simple reason is because it shows the core strength of the person who is able to show abs. It not only shows that basic core muscle strength of the person carrying those abs but also immediately shows the average percentage body-fat of the person with those abs.
Sociologists will tell you that all females have a deep seated instinct for looking for the perfect mate and when you are trying to get attention from the opposite sex as a male you need to be able to show your assets. These assets are best displayed by showing the thickness and depth of your six-pack.
But you could have a massive six-pack that would impress any female and if you or they are unable to see it because of the fat layer covering your stunning abs then it is obviously not something that is going to be seen. What this means is that you need to take control of your body-fat percentage.
Probably one of the many reasons why females think that a six-pack of abs is so attractive is because it also tells them a lot about the owner of those six abs that they might be looking at. It tells them about the discipline, power and control that you as a male have over your life, your body and the world around you.
It is these secrets that a female is always looking out for. This is something that has been going since humans have been on earth and this is something that goes way beyond and social habits or peer pressure. It is pure instinct and a female will be attracted to a good set of abs.
For information on how to get 6 pack abs fast go to How To Get A Perfect Six-Pack Of Abs ASAP