A newer test case has to be verified against several test suites. Sometimes, these suites are blocked because of an offending test case and this prohibits the user from validating if the newer test case is working fine or not. This might block the user from making further progress on the task.
These test-suites could be run with the resmoke CLI but running locally does not provide the same level of guarantee, consider the case of validating the test with whole-cluster-passthrough.
So, evergreen could enable the override option for non-admin users only for patch-builds. Keeping this option open for patch builds should be harmless.