First reason - Women love guys with ego and self confidence!
In the nature the female is always going with the strongest male. Human aren't so different. Women are also attracted to strong and confident guys that will make them feel safe! You probably think that we are smarter than animals and have mind, but attraction it's a sort of an instinct and women (and also men) can't control it! So if you really won't to become more attractive you should work on your self confidence!
Second reason - Jerks are playing hard to get!
Here another instinct that is working - we always want what we can't have. You probably know that almost all the girls in college are charmed by those popular guys who sleeping with all the hot girls in campus! Why it happens? Because they think those guys will never give them a chance! But the nice guy are always available, they are always there and will never say no! The girl just gets bored with a nice guy because she feels like she already has him. My tip to you is to learn how to say "No" to a girl - actually it's not so hard and trust me women also don't want a guy who is always says yes! Also don't call the girl 10 times per day just to ask how she is. Let her miss you, let her call you, let her chase you! Than she'll want you!
Third reason - Women want a guy who will take the lead!
When you call the girl to ask her out, how it sounds? Let me guess - you are probably asking her where she wants to go, what she wants to do and when she will be ready -right? If it's your case than you have something to learn! On the first date you never ask the girl that kind of questions. As long as you are the man - you are making the plans and the decisions. You know why? Because women have a hard time to make decisions. Have you ever though why they can spend 4 hours in a bikini store and still leave with empty hands? Because they just can't decide. So when you are telling her where and when you'll pick her you are actually making her life easier. She also will see that you are confident and it will increase her attraction to you!
As you can see attracting women it's not a rocket since and everyone can do it. I didn't mention the look on this article and I can say why. The look is just less important than the 3 things I mentioned here!