You are drastically underestimating the level of danger a criminal presents. First of all, they are ready to damage your property to the point where it puts yo

You are drastically underestimating the level of danger a criminal presents. First of all, they are ready to damage your property to the point where it puts your life in imminent danger. A car without the converter might still drive, maybe with a light on the dashboard and a loud noise, while ejecting hot exhaust gases under the passenger section and straight towards the fuel tank. Some diesel cars periodically inject unburned fuel to clean the filter at temperature over 900K. A fire in the passenger section is a distinct possibility, but imagine even just the panic response of someone who thinks they are on fire while running on the freeway. So whoever is interfering with the safety of your car already has little regard for your life. Secondly, they are risking a long prison sentence for something that's worth a few days of unskilled labor. So they have decided they won't even spare a few days of their life for the value they can steal in 10 minutes - let alone years in prison. If caught in the act, they will most certainly not put their tools down and say "Oh, you got me, darn, I guess we need to call the police now". They are by definition ready for violence, and they WILL use force against whomever attempts to retain them. So a law abiding individual has a choice between confronting a violent criminal, by all accounts ready to kill them, and not protecting their property. It's a violent blackmail, and one solution, unless we want everybody's catalitic converter to be stolen, is to balance the violence disequilibrium and make it much more riskier for the thieves.