The problem is that not all absences are reported beforehand. So you have
1. People who are here on time as expected and don’t report anything.
2. People who are here on time because they were able to join despite reporting an absence (meaning that people from reported absences have to be tracked).
3. People who are absent and reported so, which is great.
4. People who are absent without leave.
Reporting your absence is useful because it helps planning, and when you have a permanent assignment is the polite thing to do. But formalizing the reports are a lot of work.