I agree with you, however, we are talking bleeding heart liberals here. They’ll try and find some way around it. Wait for the lawsuits to start when someone is fired for engaging in what is now a legal activity. (I understand alcohol is legal and you can get fired for being drunk at work. But we are talking about liberals).
Some things absolutely require your full attention, and the requirements were introduced not as a legal issue, but one of safety.
The injury/death statistics from the industry confirm that the practice of requiring drug tests (and post accident data will doubtlessly confirm) that it is a lot safer to have straight and sober people on rig crews.
If you want to make the paycheck, make the grade.
There are quite a few other jobs which should have similar requirements, if they do not already, as a term of employment.