The night shift is appealing to many people for several reasons. It tends to have a more laid back atmosphere. Even when you are busiest during the rush before midnight, things tend to settle down in the earlier hours of the morning even when you have lots of patients to manage.
The night crew is usually great to work with, at least in most places I have been. It also usually offers better pay and provides a lot of experience, particularly for new graduates, that are looking for hands-on high volume emergency work.