They don't care what the "crime" was, a criminal record just disqualifies you. It's the same kind of HR idiocy that would forego hiring someone who has 5 years of Rails experience but did not list HTML as a skill, because HTML is in the checklist.
The reason for that is because HR departments doesn't know the difference between RoR and HTML and therefore doesn't think someone lacking the latter is capable of performing the job. Ignorance in other words. Are you claiming it is the same kind of ignorance that causes companies to not hire weed smokers?
I think both have the same root cause: not ignorance but laziness. Bad HR people tasked with filtering resumes don't want to hire the best people, they want to do as little work (and as little thinking) as possible while appearing to do a useful job.
So they just love rules that filter a lot of resumes, can be applied without thinking and make superficial sense. Understanding how skills relate is more work than comparing lists, looking at the specifics of a criminal conviction is more work that just using it as a binary exclusion criterium.
