The whole point is that the people are supposed to be trustworthy and that they do the right thing when nobody is looking.
That's why not everyone can get a security clearance -- a lot of people are not trustworthy. No one who supports Trump should have a security clearance. The attack on Jan 6 was an attack on the U.S. government. And anyone who supports such a treasonous act should not have a security clearance.
I believe Berger got caught because he took a specific document and there was a record of that document missing from the National Archives. In most SCIFs, there are no such records for documents, unless they are permanently kept in safes.