Core problem: how do you measure effectiveness of deterrent methods.
Actual or avoided incidents? Feeling of safety of the public? Most likely how happy the insurance companies are afaict
Well us who like the scientific approach would have incrementally added layers to the security onion, but in the real world, that kind of trial and error costs human lives.
Makes testing expensive
To be fair they don't even have non-lethal armaments, but it does again point to how useless the operation is in the face of a person who isn't just mad because their flight is delayed.