I thought drug testing was only done once, during the hiring process. If they’re drug testing on a regular basis that’s something entirely different. I would not support that unless the job actually required operating heavy equipment (including cars) or dangerous tools etc.

My former roommate is a drywall taper contractor and he’s told me many stories of people showing up to a job site high on meth and making a huge mess, causing dangerous accidents with tools, dropping heavy objects off unfinished upper floors etc. They definitely should be drug testing these workers regularly but they aren’t. He himself smokes cannabis but never when he’s at work. I would be fine if they tested for harder drugs but not cannabis. They should be conducting sobriety tests at work too though, as he’s also seen people show up to work drunk (though the foreman often notices this and sends them home if he’s any good).