Automotive dealerships
Over the last decade cars and other vehicles have become more expensive, with a lot of sophisticated electronics crucial to the operation as well as to provide additional features.
Many dealers do have the right equipment which is very expensive for a good diagnosis, but many independent shops cannot afford the tools, and resort to guesswork to repair a vehicle.
For many vehicle owners , their car is an integral part of their life, and they will be willing to pay whatever is needed to get it back in working condition. So they will allow the mechanic to replace one part at a time, even though the part is in perfect working condition.