Yes, you do! Even if you brush and floss every day, there are still areas of your mouth that you cannot reach with a toothbrush and floss. Plaque and tartar can build up in these areas, and only a professional teeth cleaning can remove them. Regular teeth cleanings can help to prevent gum disease and tooth decay.
In addition, your dentist can check for any other issues that may be developing. Staying current with your oral hygiene will limit the amount of dental work you will need in the long run.