This responsibility is important because it can get important information to people. Let's say that the office calls to tell a specific person that their mom is not taking them home so they will have to walk home. If that student didn't get that information, he or she would probably be freaked out that their mom is not at school yet picking them up. The phone could also be to announce that you are going home for lunch. If you did not come home for lunch, your parent(s) would be scared that something happened to you. You also would not know what to do because you don't have a lunch.
A tip to make this job more successful is to not rush to pick up the phone. Don't make it into a game to see who can pick up the phone first. Previously this year, i've seen people literally run to the phone. This could give away our right to pick up the phone.