Developers use version control systems (VCS) in collaborative projects to manage changes to source code efficiently. VCS, such as Git, allow multiple developers to work on the same project simultaneously without conflicts, providing a history of changes made. This capability enables teams to track modifications, revert to previous versions if necessary, and collaborate across different locations seamlessly. Additionally, VCS fosters better communication and documentation among team members, ensuring that everyone is on the same page and reducing errors during development. Overall, VCS enhances project efficiency and code integrity.