Having the link to your public Version Control System (VCS) in the META files help others to contribute to your code.
Having an explicit link to your bugtracker/issues in the META file help people know where to submit bug reports.
Having Continuous Integration (CI) configured helps the author catch regression and platform incompability much faster.
Having license information in the META files can help people automatically verify that they use only approved licenses.
Having your own CPAN Dashboard is cool.
No means the author does not have public VCS and does not want to have one, or that the author is not interested in CI (for at least some of the modules).
