Judges do their best, but parenting can be one of the most difficult decisions for judges, who are generally not well-equipped to make these types of decisions. 
The reason is that parenting is not a legal question inasmuch as a socio-psychological one. Most judges are not trained in parenting concepts. They are not experts in coming up with post-divorce parenting arrangements that work. They can mimic what appears to have worked in other cases, but cannot observe interactions between children and parents, and cannot be present when their decisions go into effect. Judges basically do their best having very little guidance. Because judges recognize this, they often ask a parenting evaluator to undertake an investigation and make a recommendation. Often, there is no good or clear answer, so the recommendation is based on what seems might be okay. The judge gets that recommendation and hears the evidence and make the decision.