Outside of jobs where it's pretty easy to hurt someone if you're intoxicated (construction, etc.), my personal theory is that it's all about control.
As far as I know companies use piss tests, which don't detect most hard drugs after a few days. They detect pot for weeks. Hair tests will detect anything forever. They are more expensive but if companies actually cared about not hiring people who do hard drugs they would have to do them.
The only purpose I can see for it is that it is a legal leash they can tie to the employee to exert control on their lives. There's lots of other things companies would like to be able to fire you for, but they're either illegal or impossible to detect. Drug testing is one they're allowed to do.
I can understand drug testing people if they cause an accident, are intoxicated at work, etc. but to do it as a matter of course for employment is just to show you who's boss.
As far as I know companies use piss tests, which don't detect most hard drugs after a few days. They detect pot for weeks. Hair tests will detect anything forever. They are more expensive but if companies actually cared about not hiring people who do hard drugs they would have to do them.
The only purpose I can see for it is that it is a legal leash they can tie to the employee to exert control on their lives. There's lots of other things companies would like to be able to fire you for, but they're either illegal or impossible to detect. Drug testing is one they're allowed to do.
I can understand drug testing people if they cause an accident, are intoxicated at work, etc. but to do it as a matter of course for employment is just to show you who's boss.