Updating a dependency generally grants you some benefits:
- New features;
- Bug fixes;
- Security updates.
Even if you are not actively adding new features to your application, it may still be affected by bugs or security vulnerabilities caused by its dependencies, which may be fixed by updating to the latest version.
In addition, while there may be no planned further development now, there might be in the future. In that case, updating dependencies on a regular basis ensures there will not be a significant amount of technical debt if a new feature must be added, or a new bug is found and requires to update a dependency. This is a judgment call your organization may make depending on the situation.