While almost all contested divorce cases settle, not all do. There are some cases that just have to be tried because the positions are too far apart whether it be for residential custody, valuation of assets, determining income for child support or many other issues.
Sometimes having a trial date is needed just to make the other side come to the negotiating table because without the fear of a trial, the expense and time, one side may be perfectly content leaving things the way they are. There are cases in which one parent is in the house, the bills are paid by the higher income earner and the parenting schedule is perhaps less then what it should be. The parent in the house is in no rush to move the case along so that upon resolution, whether by trial or settlement, they get less money and less time with their children and have to sell the house.
If negotiations are stalled or the numerical differences are too great for compromise, for example does the person earn $300,000 or $600,000; is the business worth $2,000,000 or $4,000,000.
Many judges will give the attorneys a range as to what they think is a fair resolution without pre-judging the case, of course there are times where the attorney may feel the judge has not had the benefit of hearing and seeing the witnesses and the attorney believes that his client will sway the judge. However, most cases should and do settle however some will not without a trial date bearing down on the parties and their attorneys.