Thing is, you as a small shop don't care... but large corporations, they get so many applications that they use background screening to filter down the load to something that their HR can handle, and in some cases (especially in government, aeronautics and medical) client contracts require regular checks of employees.

If they’re already filtering on things unrelated to the job, they could just as well throw out whatever percentage of applications was needed to get down to a load their HR could handle.

the things unrelated to the job are things they can then say are related to moral character and make you a better hire overall.

Also any prior arrest record - DUI for example - can affect your permissions to work on projects with high security clearances and thus a factor that might not be relevant to small shop would at any rate be potentially relevant to large corporations who are the ones getting government contracts that require high security clearances.

It fine to think that way. The problem is restricting other peoples right to free association if they do not want to hire them . Having a DUI is not a protected class.