I hate with all my passion recreational drug users or to be more precise, of those who make their behaviour known or otherwise affect my life.
However, for the purpose of employment, drug testing is needlessly intrusive in all but a few special cases. It is just simply not needed and risks creating far more problems than it attempts to solve.
Going down the path of money trumps all other concerns or "perfect market results in perfect results", you would soon arrive at a "Gattaca" situation and beyond where unless every single DNA base you possess is perfect, every behaviour is perfect from birth, everyone you have ever networked with is similiarly perfect, etc., you will never be employable or move beyond a specific bracket alloted to you by society. In the meantime, costs to existing businesses and challenges to entrants would skyrocket in a self-defeating spiral, while incredible talent that may suit your company dies by the wayside unused or misallocated.
Drug testing and much more, as technology now and in future allows, may be fine for the cutting edge of physical endeavours or positions of massive responsibility for human individuals where even a second of downtime could make or break a company, but for anyone else, that is well beyond reasonable.
A basic analogy in one respect would be like applying military critical software certification standards and testing for bug-free processes (the kind that causes operating systems and software designed in the 70s to still be used) in all software ever produced from now...