In further news; might as well never get a haircut, tons of people get bad ones, never go to a restaurant who knows how much spit (or worse) you'll eat, never go to a bar, saw a TV show where a guy goes and finds rats, roaches and fake expensive booze in there.
Most won't beat the snot out of customers cars (95% or so of mechanics I worked with wouldnt the few that may were fresh out of high-school were the ones who 'may') and if they did do anything dumb they were fired on the spot. Did I mention most 'reputable' shops(and even your disreputable shops) have insurance as a requirement of running a business. You know what happens if a tech wrecks a car? Shop pays a deductible and tech takes a walk. "Oh noes, don't drive my car, you might hurt it" every single instance I know of where a shop damaged a car (wreck, negligence, fires, fall off lift) the shop footed the bill 100% without much trouble.