Requirements coverage is not one of the three reasons why trace requirements are useful. Requirements coverage is a measure of how well the requirements address the needs and objectives of the stakeholders and the project. Trace requirements are useful for the following three reasons:
Requirements allocation: This is the process of assigning requirements to the components or deliverables that will satisfy them. Trace requirements help to ensure that each requirement is allocated to the appropriate component or deliverable, and that no requirement is left unallocated or over-allocated.
Quality control: This is the process of verifying that the requirements and the deliverables meet the quality standards and criteria. Trace requirements help to ensure that the quality of the requirements and the deliverables can be assessed and validated, and that any defects or issues can be identified and resolved.
Impact analysis: This is the process of assessing the potential effects of a change request or a problem on the requirements and the deliverables. Trace requirements help to determine the scope and magnitude of the impact, and the actions needed to address the change or the problem. Reference: Certification of Capability in Business Analysis (CCBA) - Simplilearn, Module 5: Planning and Monitoring, Lesson 5.3: Estimation; Business Analysis Techniques - ECBA, CCBA, CBAP Endorsed, Section 8.3: Requirements Traceability; Intro to the Certification of Capability in Business Analysis (CCBA) - Pluralsight, Course Overview, 2:00-2:20.