Some girls with low self-esteem feel that they have to change themselves to find love. If they are nice they throw away their morals and values because society tells them that they have to loosen up if they want to find love.
Being easy will not help you find love. Sure you will get a guys attention, but it will only be for tonight. It will not make him love you and want him to spend the rest of his life with you.
When a guy sees a girl who is extra flirty he will feel that she is with that way with most guys. He will not want to take her home to meet his parents he will not even considering marrying her.
Guys talk and sometimes what they say is not so good. By being easy you give yourself a bad reputation. You will get called bad names and guys will not respect you.
When you give in easy guys will leave. They will see you as easy and once you give them what they want they are done with you. Then you will get hurt once they are gone, that is if you get attached to the guy and are looking for a relationship.
They will then move onto the next girl and keep finding girls to sleep with. Then when they find a girl who is good and who is girlfriend material they will settle down with her. Showing a guy you are easy will not make him want to settle down with you. It will make him see you as someone who is fun and not someone who wants a serious relationship.
When it comes down to the long run a guy wants a girl who has not been with every girl on the planet. He wants a girl who he knows he can trust and take home to his parents.