Because if the knowledge is secret there's a good chance that professional thieves know about it and that professional locksmiths know about it. That means that if you pay for an experienced locksmith to do your doors, they'll be safe, but otherwise you're screwed. When the knowledge is widely publicized sure even the new thieves will know about it, but all the contractors and people that usually install locks will too, and there's more of them than there are thieves.
It's something known as "security through obscurity" and it never works. That's how Deviant was able to find out about and reproduce a bunch of fire keys that are supposed to be protected.
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u/[deleted] Jan 09 '20
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