Even the testers who are not fooled have to worry about lawsuits and proving a positive case if it goes to court. Almost all testing is done with urine, not blood. Most experts agree that blood testing is more accurate than testing urine and that some of the drugsthat are undetectable in urine can be found in blood. But blood has too many problems, as it clots and spoils, it has to be kept cold, and it would be against the religious beliefs of many. Most people just don't want to handle it because of contagious diseases, broken vials, etc.
Blood is just a major headache to deal with.
It is also a lot more expensive, not to mention the possible civil liberties lawsuits, as taking blood is considered a lot more invasive to someone's body. Many governing bodies may also fear that ifthey switch to blood, the number of positive tests would rise sharply. This would hurt their public image, not to mention their big bucks corporate sponsorships. Drug testing is also expensive, so lower level competition can't even afford it. An athlete could use drugs for several years before having to take a single test.