So funny story about this
When I started working at my current company (tech company, where I do tech things), my pre-employment paperwork required me to agree to a drug test (though none was actually administered). I was surprised by this -- never had to agree to this before -- but at my wife's counsel (in both senses of the word -- she's an attorney -- agreed because I didn't want to be "that guy").
About a week after I started, I was idly talking to our security guy and mentioned this, and he flipped out, and sent an email to HR complaining about the inappropriateness of requiring all employees to agree to drug tests. I got a really contrite email from HR letting me know that the drug test provision was there for the part of the company that was driving for the company as their job, because insurance and the law, apparently, required us to get them to agree to drug tests, but that people who weren't driving for the company would never, ever, ever be required to do a drug test; the pre-boarding paperwork erroneously specified this for everyone rather than just new drivers, apologies, etc, and they would fix it immediately.
It was a nice way to start working here.