Some people believe that marijuana and drugs can stay in their system for up to two weeks, sometimes even a whole month, even though they haven't smoked or consumed drugs. This is one reason why they would want to refuse to take a urine test. They believe that the results will show positive and they may be arrested for drug charges instead of DWI. Even if they didn't smoke marijuana that day and they may have had one to two drinks, they could still be charged with refusing a test.