There are a ton if reason's why...
here are some of them....
Women often stay for the following reasons:
She truly may not believe she is being abused. In order to remain in the relationship, she has found ways to explain away the incidents of mistreatment, whether emotional or physical. Or, she may feel that she can "handle" him and avoid serious incidents.
Sadly, a woman often earns less money than a man, or may not work because of her partner's objections. She knows if she leaves the relationship, she will have great difficulty supporting herself. Usually, her partner has reinforced these fears, telling her that he will not help support her, or that she can never find or keep a job. He may also threaten to make trouble for her on the job, if she is employed. This issue is compounded when there are children involved.
Threats are used as an effective technique to keep someone in a relationship, which is the goal of the abuser. A woman may have been told over and over that if she leaves the relationship, terrible things will happen to her. He may have convinced her that no matter where she goes, he will find her and never leave her alone. She may also fear living alone and the prospect of trying to support herself and the children. Or he may have threatened to kill her, the children and himself. (Threatening suicide is quite common in relationships where the abuse is mostly emotional.)
A woman usually wants her relationship to work and is willing to hang in there waiting and hoping things will improve. She may believe the promises and explanations her partner offers and may feel she can't simply give up on the relationship because of a "few problems."
Whether she wants her children to have good relationships with their father, or she feels guilty "breaking up" the family, or because of his threats to keep her away from the children, many times a woman stays in an abusive relationship because of her children. Ironically, she will often leave because she realizes her children are being adversely affected by living in an abusive atmosphere.
Most religions strongly discourage divorce and the breakup of the family. These ideals are admirable, but when abuse is involved, there is little Biblical support for remaining. But, a woman who has strong religious convictions can feel an enormous guilt if she leaves her marriage.
Pressures from family or church:
Surprisingly, the family may refuse to believe there is abuse in the relationship. Abusers can appear to be very charming and likable to outsiders. Sometimes, when a woman turns to her church for assistance, she is told she must stay in the marriage, because of her vows. Fortunately, these attitudes are beginning to change with a greater understanding of the horrible effects of abuse.
No place to go:
By the time she decides to leave, her abuser may have succeeded in isolating her from her family and friends. She may feel she has nowhere to go. She may be embarrassed to ask strangers for help and reluctant to go to a shelter, if there is one available.
Men often stay in abusive relationships for the following reasons:
Yes, men can be abused, too, and not because they are "wimps." Although the situation is somewhat different and usually involves mostly emotional abuse, and even though it is usually easier - financially speaking - for a man to leave the relationship, men often stay for various reasons.
He may feel her abuse is caused by her emotional personality, PMS, or other hormone fluctuations. He decides to ignore her abuse because he loves her and wants the relationship to continue
In spite of the abuse, he may find enough good in the relationship to "make up" for the abuse.
He may stay, not because he wouldn't be able to support himself, but because of the prospect of paying child support and alimony or dividing the marital assets. He may choose to stay until the children are grown and then leave.
While a man may stay out of fear, it is more often fear of what she will do to herself, rather than what she might do to him. Abusive women often threaten suicide if her partner leaves. Additionally, she may have threatened to make trouble for him at his job.
It may be easier for a man to avoid or ignore abusive incidents if he has a demanding job, or reasons to be away from home regularly.