Because, for someone with any kind of security clearance, suddenly going out to the woods, if you don't normally go out to the woods, would be a major outlier from your highly-scrutinized and documented regular life; and so could easily lead the FBI to finding your buried gold, without having to get any kind of warrant.
Isn't the FBI investigating deaths and disappearances of people with critical access to sensitive material and only found out about it from a newspaper? How much resources do you think are put into monitoring every aspect of the lives of people with access to sensitive info?
https://www.cbsnews.com/news/deaths-disappearances-scientist...
Nonsense the cost of physical surveillance is extremely prohibitive.
The security scrutiny is really so thorough that taking up a new apparent hobby gets flagged? That’s impressive.
I think you're overselling the security clearance system.
In reality, it'd flag something like "taking out a massive loan for no discernible reason", or "filed for bankruptcy".
I believe a huge part of the big AI push is that the government dragnets have collected so much data, it's nearly impossible to sift through and they're hoping LLMs can finally make sense of it, along the lines of what you're suggesting.