The cost of leaving is just the initial reason 'why', but it doesn't begin to touch the deeper aspects of what 'just leaving' really means.
Often women who leave will decide to head into shelters for some measure of protection. This can help in many circumstances, but when moving into a shelter these are common issues encountered:
1. living with room mates they don't know,
2. leaving their own community
3. allowing the government to dictate many basic choices for their children,
4. agree to attend many meetings to meet the requirements for assistance,
5. share intimate aspects of their lives with strangers,
6. work with attorney's that are assigned to your case when necessary
7. the costs involved with replacing everything they need,
8. leaving behind family pets due to new living arrangements,
9. navigating ongoing requirements of the police for physical protection,
10. finding medical coverage for themselves and any children involved,
11. addressing any transportation issues
12. often new schools and/or friends for their children,
13. depend on complete strangers for basic necessities
14. lack of housing options
15. lack of adequate finances to support independent living
Leaving is starting a new life at the drop of a hat and this option is not always easier than putting up with a few arguments. The arguments do have a cost involved, but the environment they live in is known. This means the victim has a general idea of what that cost looks and feels like most of the time. If she chooses to leave there are a million unknowns.
Even with the number of issues listed here I didn't even touch on the emotional aspects of leaving someone you love dearly. A person who chooses to leave is walking away from one of their most important relationships, and this means there are many emotional issues involved in choosing to leave.
"Just leave" shouldn't even be a phrase anyone uses when talking to or about an abused individual choosing how they are going to cope with the domestic violence they are dealing with.