A disability hearing is one of the most critical stages in your appeals process. While it is not required that you attend in person, it could be critically important that you do so. So yes, you have to attend your disability hearing.
Remember that the disability hearing gives you face to face interaction with key persons who will decide the fate of your case. The administrative law judge (ALJ) assigned to your case will be able to ask you questions and hear your side of the story. You will be able to provide evidence about your eligibility for benefits, and will be able to tell the judge in your own words why you believe that you qualify for disability benefits. You can present your account of your condition to your judge, and persuade him or her about the severity of the symptoms which restrict your ability to work.
In some cases, the judge will be able to see firsthand that you indeed do suffer from the limitations that you have claimed in your appeal. For instance, if your claim is based on mobility problems, musculoskeletal problems, chronic fatigue, or other problems that are easily apparent, the hearing will give the judge a chance to see how your condition limits your ability to perform substantial gainful activity and earn a living. If you stay home and are absent from the hearing, you are depriving the ALJ of the opportunity to take notice of how the symptoms affect you. This could be crucial to the success of your claim.