How does multitasking make it difficult to accurately resource level a project?

Multitasking complicates resource leveling in a project because it can lead to unclear workload distribution and prioritization among team members. When resources are spread thin across multiple tasks, it becomes challenging to accurately assess availability and capacity, often resulting in over-commitment or underutilization. Additionally, the constant switching of tasks can reduce overall productivity, making it harder to track progress and allocate resources effectively. Consequently, this can lead to delays and inefficiencies in project execution.