The call diversion can increase someone's availability to the caller. The main alternative is an answering machine or Voicemail, but some callers do not want to leave a recorded message, suspect that parties will delay returning their message. You can transfer home phone to cell phone in USA to get best services.
Some businesses find that human touch can increase contact, thus sales, but traditional cable answering services are traditional expensive, so they receive their calls to the call center, so clients can reach operators instead of answering machines or voice messages. Before the availability of call forwarding, the commercial answering service is needed physically connected to each line they provide response after hours; It requires their office near the local center exchange and is fed with a large multi-pair rod where a pair of separate cables for each client customer. With call forwarding, there is no physical connection to the client's main telephone service, which is only forwarded to the answering service (usually on the entry dial number directly) at the end of the working day.
Often, big suburbs are toll calls from many suburban exchanges on the opposite side of the same city, although all the suburbs of this city are local calls to the city center. A business located on the outskirts of the city like that might benefit from getting the city center number as "extender", to be forwarded permanently to their geographical earth suburbs.