There are several reasons why organizations may choose to migrate to SharePoint:

1. Improved collaboration: SharePoint provides a central location for team collaboration, where documents and information can be easily shared and accessed by multiple users.
2. Better document management: SharePoint provides features such as version control, metadata management, and retention policies that help to better manage documents and information.
3. Enhanced productivity: SharePoint provides a platform for creating custom workflows and automating business processes, which can lead to increased productivity and efficiency.
4. Better access to information: SharePoint provides access to information from anywhere, on any device, which makes it easier for users to stay informed and make decisions.
5. Increased security: SharePoint provides a secure platform for storing and sharing information, with options for data encryption and access controls.
6. Integration with other Microsoft tools: SharePoint integrates with other Microsoft tools such as Office 365, OneDrive, and Teams, which can provide a more seamless user experience and increased productivity.
7. Scalability: SharePoint can accommodate the growth of an organization and can be scaled to meet the needs of small, medium, and large enterprises.

In summary, If you are concerned about your old file-sharing server on-premises for many reasons such as OS and hardware aging, storage space issues, etc, migrating to SharePoint can help organizations improve collaboration, document management, productivity, access to information, security, and scalability.