Credibility and Endorsement: It offers an endorsement from respected individuals or organizations, significantly enhancing your project's credibility. 

Demonstrates Collaboration: It indicates that your project has the backing of key stakeholders, highlighting strong collaboration and support from the community or relevant partners. 

Highlights Relevance: These letters often emphasize the importance and relevance of your research within a broader context, aligning your goals with community needs or organizational priorities. 

Strengthens Grant Applications: For grant applications, letters of support can be crucial. They help to present a comprehensive picture of your project's potential impact and feasibility, making your application more compelling to reviewers. 

Resource Commitment: They can also show commitments of resources, such as funding, facilities, or expertise, which are vital for the successful execution of your project.