You meant to say "why would you need negotiation"? Well negotiation is what avoids violence or depression when a conflict arises, and conflicts always arise.
Discussion
The negotiations should happen before your married. Basically establishing a mutual understanding of who has the final say and what the roles are. It shouldn't even really be a negotiation. If the woman has been lead my a strong father then she will find her role naturally. Only with modern women do you have to be so explicit
Negotiation is what avoids violence... between MEN.
Any man that needs to bargain with his wife in regards to decision he is ultimately responsible for the consequences of needs take back the pants in the relationship and give her a summer skirt and a very difficult conversation.