It's a common thing for "mechanics" at tire shops to threaten to not let people leave because of various issues. I've known people its happened to. It is not the mechanic's (tire changer's) job to confiscate people's vehicles, period. Attempting it will bring about a lawsuit alot quicker than some hypothetical liability issue. It's just a way for greasy tire salesmen to strongarm people (generally women) into a sale.
*when I say 'greasy' I don't mean like oil and grease greasy. I mean like scumbag, just to clarify. No shame in being a grease monkey, I am one myself.
There really should be inspections in every state. I've fixed cars with 4 tires with steel belts showing on the edges. That car should in NO way be allowed on public streets. The last one was a white BMW, I'm sure the tires were 300 bucks apiece for crappy ones. Not my problem. If some asshole kills my wife by driving that car on the freeway and causing an accident....no lawsuit is coming. Something much much worse.
Yeah I would say the cons of having another govt agency policing people's tires outweigh the pros. Especially given the low percentage of car wrecks that are actually caused by tires. Most passenger cars and trucks can handle a blowout just fine, it the big semis and heavy commercial vehicles that tend to lose control in a blowout, and most of those vehicles are already subject to DOT regulations and inspections. Shit, i had and pretty sweet Acura when I was younger with the low profile expensive tires (probly like the ones on the beamer u were talking about), i had a tire blow out on the interstate and hardly noticed. Slight wobble is all, the smell of burning rubber from the tire wear is actually what prompted me to pull the car over. Another time (same car) one of my front tires looked low, I checked it and it had less than 10 lbs in it lol. You could barely notice.
Exactly why they should do inspections. People don't notice.... I have to have a 3 year old car with no check engine light emissions tested, have every year after the initial registration. An emissions tech could at MINIMUM visually check all 4 tires and flag your car for inspection. Would cost the government next to nothing.
