why are some fastfood places slow?

A job at a fast food restaurant is a very low paying job, and you're right many of the employees don't want to work there. Some don't want to be working at all. They work there because they can't find another job, or they take the job until they can find a job more to their liking. However, this does not excuse rude behavior. When a person takes a job they should do the job to the best of their ability and cheerfully. If they would change their attitudes and be thankful they have some income coming in, the time at work wouldn't be so tedious.