Children are way too young to fully comprehend the concept of divorce; what good would children do anyways? Moreover, divorce can be a traumatic experience especially for younger kids; I feel that instead of worrying for their parents, they should be out there enjoying their childhood. Like everyone else mentioned here, there are also other factors contributing to divorce, such as an uncommitted partner or cheating; children will most likely not know that and would be better off not getting a say in their parent's divorce.
Uhm if your in an abusive relationship and the child does not know about it, they may not know why the parents would want a divorce. I mean kids should definitely say what they think, but if they have no idea in whats going on, then they should keep their mouths shut.
I fully understand that children are directly affected by their parents' divorce, but there are a lot of factors that go into an adult relationship that the children may not or should not be aware of. If one parent is abusing another parent, or if a parent have been unfaithful, the children are not likely to be cognizant of how that affects the other parent or how it may affect them in the future. The children have a desire to keep the parents together – even if it means endless pain and misery for the parents.