There are a couple of reasons.
If the person to be served is a relative, we would have to go back to confirm the relative still doesn’t live there. In this day and age, many children move back in with their parents or siblings, so we cannot assume the relative no longer lives there. While a deputy is assigned a specific area (sector) of the county to serve, he or she may not necessarily work exclusively in that sector. Deputies often cross zones to provide timely, efficient service, especially when their partner is off.
Therefore, you may have told another deputy that the person he is seeking doesn’t live there but the current deputy would have no knowledge of the conversation. We very much appreciate it when the resident/occupant calls to provide us with this information.