There are a number of reasons why this should be so. Let us look at three of the most important reasons.
First, there could be the fear factor. It is a sad fact that men will relatively often harm or even kill women with whom they have been involved. If women have been abused, they may not want to press charges for fear that the men will take physical revenge on them.
Second, there is the fact that women who are abused often feel as if they are still in love with their abusers. They do not want to press charges against them because the men are still important in their lives. This may be due to a lack of self-esteem that makes them feel that they would not be able to find another man to love them.
Finally, it is possible to argue that our society teaches women that domestic violence is their fault. Women who have been abused sometimes feel that the abuse only happened because their men loved them so much and they did something to ruin the relationship. They feel that they do not want the men punished for a mistake that they (the victim) made.
Of course, not all victims of domestic violence feel all/any of these things. There are many women who stand up against their abusers. When victims do not press charges, however, these are likely reasons.