I get your point, but it's not entirely true. I work int he entertainment industry. I have for both music and film. They do not drug test executives, and they make bank. I think the only potential drug tests would involve only those who use heavy machinery in production or on tour.
More and more companies do test, but not all. It's probably the exception that makes the rule.
Also having worked in property management, publishing, and electronics...never was there a test. Only when I temped at a utilities company did they test. My wife, for teaching, does get tested. I tend to think many govt. jobs do test from my understanding.