I work for the US Post Office. In my town it takes 6 people to run it on closed days. This includes the 4th of July. All holidays. There are many businesses that do not take holidays off. The Armed Forces is a BIG one. Not everyone can take holidays off and still have America be America. If the world took holidays off we would be in big trouble.
Be glad you have a job, even if it is on the 4th of July.