The largest advantage of having a landline telephone is reliability. In the event of a power outage or weather event, landline telephones can often remain functional when other types of phones do not.
Those living in remote areas may not have access to cell towers, making a landline phone the only option as well. Emergency services is another reason to consider having a landline telephone, as 911 services are often better able to locate the service address via a traditional telephone than with cellular service. Costs of service can also be a factor, as standard telephone service is often cheaper than a cell phone.