For Shelter City, it's quite easy to strictly inspect smuggling due to its size.
As long as the caravans register all goods when entering the checkpoint and verify with the registration form when shipping out, any smuggled goods can be easily identified by comparing the two.
However, the reason no Shelter City chooses to do this, and instead allows caravans to trade freely after passing inspection, is primarily because every shelter city that has tried strict checks in the past has without exception been blacklisted collectively by the caravans.
Firstly, the 20% inspection tax is actually an incentive for gambling.
Wasteland caravans have always been profit-driven; without enough profit stimulation, no one would risk being attacked by Infected Bodies, mutant creatures, and raiders to travel trade routes.
Simple normal goods trading cannot continuously attract caravans.
Even at its peak, Happiness City had to offer an additional 5% profit as an "incentive."
