Often a couple will bear a child and then split up under acrimonious circumstances. Although this is the case and the mother and father bear ill will toward each other, the remaining parent (or other parental figure) doesn't want to poison the child's mind against the other parent. Or they really would prefer not to have to admit to the child or anyone else that they were abandoned/left. Or one person will abandon the relationship leaving the other hurt. But still, a child is an innocent. Or the missing parent is in some sort of special circumstnace, regardless of feelings on either side.