This type of request can have a significant impact on what happens during the trial. The reason is that the issues that are brought up before trial are known to be problematic. If the judge issues a clear-cut decision, then the attorneys know exactly how to deal with that legal issue during the course of trial and can plan accordingly.
The trial judge will sometimes wait until the evidence or testimony is actually presented during the trial before rendering a decision. In addition, if the judge does render a decision prior to trial, it is vitally important that the attorney preserve his or her rights in the event they need to appeal that decision.