Drug testing is absolutely a good idea for jobs where worker impairment presents an imminent physical danger to lives and property (e.g. trucking, medical professions, powerline repair crews).

Likewise, limited use of criminal background checks may be a good idea for certain jobs (a bank robber shouldn't be allowed to work in a bank).

But the idea that these should be general conditions of employment across all industries is a problematic one. It creates an underclass of unemployable people, forcing them to become a drain on society when they could be productively employed (or encouraging them to become productively employed in gray/black market activities).