These campaigns are rarely focused on the national issues about which we care so much, but they are still important. If you can help a good person win a lower office, that person may be running for higher office in the future. That run sometimes starts with that first city council race.
Even if the candidate isn't important, your help in the race will cause people to notice you. The local party will appreciate your help. That doesn't mean that you can dictate policy to anyone after having helped in one campaign. However, you will develop influence over time. Someday, if you want to take a shot at an office yourself, you will have built some support. Maybe you will be the person who runs someday to do the things that you wanted Duncan Hunter to be able to do.
Bill