Surely, occam's razor applies here. Low level workers have the highest chance of getting injured while operating heavy machinery -> highest chance of being dru

Surely, occam's razor applies here. Low level workers have the highest chance of getting injured while operating heavy machinery -> highest chance of being drug tested by the police in such cases -> the management would rather spend money on drug testing than on the lawyers later on. High-paid workers have a pretty small risk of injury -> very small risk of the government testing them -> management is not incentivized to spend money on drug testing (and possible hiring costs later on).