Types of Leaves
I believe there are two sets of leaves:
1. SICK/CASUAL: These kinds of leaves are a right of the employee and are provided once a month generally. So, you cannot stop anyone from taking such leaves. However, reasons justifying such leaves could include medical/family urgency, etc.
2. Earned Leaves: These kinds of leaves are earned by the employee, so rules can be implemented to prevent their misuse. For example, avoiding clubbing them with weekends or during business exigencies. However, the manager should make decisions on a case-by-case basis and not treat each employee exactly the same.
Most leaves are usually planned according to the convenience of all family members. It is important not to restrict employees from taking leaves. Therefore, it may be beneficial to schedule significant tasks from Tuesday to Thursday to avoid impacting delivery schedules, meetings, etc.
I work in IT, and we often encounter such issues. People who travel on weekends are generally less enthusiastic on Mondays, which can negatively affect productivity.