Almost all churches track worship attendance to give leadership an idea of the effectiveness of their large, celebration gatherings. Generally, a single number represents the attendance each week or in some cases for each service, each week. These are then plotted over a period of time to track engagement and see trends. We all know this.
Sometimes individual attendance is tracked in worship in order to reach out to people who miss multiple times. This works fine for really small churches, but larger churches empower their small groups to shoulder the burden of care.