You got some...interesting replies. I think it's mainly a CYA/insurance thing as well as a simple test to weed out undesirable traits. It's generally well known that you'll be tested prior to hire (at least in the US). My view is accept that and either
I was confused by this part of the article. Are 23% of candidates being screened at the interview phase, or at the pre-job-offer phase? Drug screening isn't a cheap thing that you just do to everyone that walks in the door.
My company puts a common clause in the offer letter that says "this offer is contingent upon your successful completion of a drug screening, confirmation of your references, and the verification of your education and work history".
Lots of companies have services where their employees are contractors to other companies. Other companies can require the services co to screen all their contractors for drugs as a part of liability coverage.
For example - if you work for a company that provides contract services to healthcare / hospital / gov / dod companies or agencies - you will likely be required to take a drug screen. and this is done prior to your offer being officially accepted on their end.
a) stop/pass the test
b) find somewhere that doesn't care