> (1) both sides have a decent chance of winning, or (2) one side - or both - hate each other so much that they refuse to settle.
There are three other categories of cases you missed and (1) can and should be divided up further into two categories. The third situation arises when one party to the suit simply cannot afford to lose under any circumstances but somehow can still afford to keep paying lawyers indefinitely. Frequently you will see this with large companies fighting to prevent or delay a class action or against an adverse regulatory decision which poses an existential threat to their industry. $50m in legal bills per year doesn't even register against a multi-billion dollar class action risk.
The fourth situation is when one of the parties has a non-financial incentive to continue the litigation, often from a political perspective. For example, when Hobby Lobby in the US sued to get out of the Obamacare birth control coverage requirement. They would have spent themselves into the ground on that case because the principle mattered more to the litigants than the cost.
The fifth situation is when one or both parties have bad lawyers. We (lawyers) don't like to admit how often this happens, but frequently one of the lawyers just completely misinterprets the law or fails to recognize essential facts. They may oversell the case to the client and then paint themselves into a corner which they can't gracefully back out of, and so drag the case out well past its proper expiration date just to avoid admitting they screwed up.
Regarding your (1) point, the evidence for both sides is roughly evenly matched in some cases, so the judge or jury's interpretation of the facts will dictate the outcome. How people weigh and interpret evidence can be incredibly unpredictable, which may prevent settlement in those cases. In other cases, the law is unclear or unsettled, whether because previous cases were poorly decided, a law was poorly drafted, or the issue is truly novel. So unclear law or unclear facts. In an ideal world, those would be the only reasons that anyone would ever go to court.
All of these situations are extremely rare. In terms of quantity of cases, unfortunately people that hate each account for the overwhelming majority, though that tends to be most common where the parties have a B2C or or close business associate relationship, or in non-commercial litigation (most visibly and notably in family law cases). B2B/arms-length commercial relationship litigation tends by and large to be a more coldly rational affair, though not without exception.
There are three other categories of cases you missed and (1) can and should be divided up further into two categories. The third situation arises when one party to the suit simply cannot afford to lose under any circumstances but somehow can still afford to keep paying lawyers indefinitely. Frequently you will see this with large companies fighting to prevent or delay a class action or against an adverse regulatory decision which poses an existential threat to their industry. $50m in legal bills per year doesn't even register against a multi-billion dollar class action risk.
The fourth situation is when one of the parties has a non-financial incentive to continue the litigation, often from a political perspective. For example, when Hobby Lobby in the US sued to get out of the Obamacare birth control coverage requirement. They would have spent themselves into the ground on that case because the principle mattered more to the litigants than the cost.
The fifth situation is when one or both parties have bad lawyers. We (lawyers) don't like to admit how often this happens, but frequently one of the lawyers just completely misinterprets the law or fails to recognize essential facts. They may oversell the case to the client and then paint themselves into a corner which they can't gracefully back out of, and so drag the case out well past its proper expiration date just to avoid admitting they screwed up.
Regarding your (1) point, the evidence for both sides is roughly evenly matched in some cases, so the judge or jury's interpretation of the facts will dictate the outcome. How people weigh and interpret evidence can be incredibly unpredictable, which may prevent settlement in those cases. In other cases, the law is unclear or unsettled, whether because previous cases were poorly decided, a law was poorly drafted, or the issue is truly novel. So unclear law or unclear facts. In an ideal world, those would be the only reasons that anyone would ever go to court.
All of these situations are extremely rare. In terms of quantity of cases, unfortunately people that hate each account for the overwhelming majority, though that tends to be most common where the parties have a B2C or or close business associate relationship, or in non-commercial litigation (most visibly and notably in family law cases). B2B/arms-length commercial relationship litigation tends by and large to be a more coldly rational affair, though not without exception.