Don't find out about until it breaks, leaving them stranded or causing a wreck. When your tie rod breaks at 80mph, if you survive, you are going to be really upset that the guy who serviced it 2 weeks before didn't tell you it was worn out/loose. And you'll never go back to that shop again because they failed to warn you of issues you didn't know about.

You take your car to a shop where you trust that the technicians are looking for potential issues. And the good ones will tell you right up front how big of a deal it is. A few places are even taking videos while it's in the air and showing you the severity of the issues so that you, the consumer, can make an informed decision about whether to get it fixed or not.