The reason they want to enter the person as soon as possible is so that any checks for that person's info will return a "hit" in time to locate the person. For example, George has dementia, goes for a walk at 8am, and is gone for several hours. He is reported missing at 12pm, and the police report is keyed into the state database by 1pm. At 2pm that same day, George is stopped by an officer and his information ran on the state computer. A hit shows up that states he's a missing-endangered person (endangered due to his mental state), the officer notifies his department so they can notify the family, and all is well. Now, if the bogus 24 hour rule was real, George never would have been reported the day he went missing, and perhaps would have met a grisly demise that night. Timely reporting is a potentially life-saving measure and I really wish television and the movies would stop it with that particularly dangerous bit of misinformation.