That's a good question. Chinese restaurants are open on Christmas because they serve Chinese food, which is a cuisine that is not traditionally associated with Christmas. In many countries, including the United States, Christmas is a religious holiday that is celebrated by Christians, and many people observe the day with religious services and family gatherings. However, Chinese restaurants are often open on Christmas because they cater to the people who do not celebrate the holiday or who may not have family or friends to celebrate with. Additionally, some Chinese restaurants may have a tradition of staying open on Christmas to serve people who may not have anywhere else to go.