I can really only understand drug testing in jobs where safety is dependent on employees being clear-headed - vehicle operators, heavy equipment, that sort of thing. Of course drug testing doesn’t catch everything, so there may be better ways to achieve that goal. For other types of employees, shouldn’t they just be judged on their performance? If they get the job done, who cares what they do on their own time?
Today most dealerships are 90% warranty and 10% customer pay. The evidence suggests the drug testing replaced employees liked by customers with employees chosen for the pureness of urine.