Earlier quoted context omitted.
I assuming they drug test because it's a requirement for govt contracts. Given that they get something like 98% of their funding from the govt, they can't exactly flippantly violate their best customers rules.
> 98% of their funding from the govt That is nonsense. Look at their flight manifest and see how many flights are NASA or Space Force. Maybe like 3 launches in the next several months out of planned 25. https://www.spacelaunchschedule.com/category/spacex/
The point is their business model is predicated on using govt contracts early, when they were an unproven commodity, because the govt is generally the only organization who can take those kinds of risks. In turn, this fosters the development of a space industry which can transition to more private revenue streams. Musk himself said they were in the 11th hour of bankruptcy before NASA "saved" them with a huge contract.