The goal of cvechecker is to report about possible vulnerabilities on your system, by scanning the installed software and matching the results with the CVE database. Indeed, this is not a bullet-proof method and you will most likely have many false positives (vulnerability is fixed with a revision-release, but the tool isn't able to detect the revision itself), yet it is still better than nothing, especially if you are running a distribution with little security coverage.
Still, the tool remains useful. With the proper reporting in place, you are immediately warned when a new CVE has been released that might match your system. You can then take the appropriate steps (acknowledge report, verify incident, fix package or mark as false positive).