It may have a seed of truth but is largely premised on anecdotal experience, operative mythology or intuitive understanding but is largely untested. If left unchecked, conventional wisdom can lead to unwarranted assumptions that disrupt the negotiation process. Negotiators and mediators need to filter their conventional wisdom for unwitting biases and misconceptions. Obtaining some of what you want.
People are greedy and want something for nothing.
They are afraid of looking like a fool and being taken advantage of. Divorce means the end of the family or failure. There is only one right answer to a problem or dispute. There may be multiple possible resolution.