Something occured to me recently as to why the polygraph hasn't already been abolished. The examiner is supposed to draw 1 of only 2 possible conclusions: truth or lie. So in general, if the examiner were to pick a conclusion at random, the examiner is right half the time. 

However, if there were, hypothetically, 3 or 4 possible outcomes instead of 2, the probability of guessing correctly goes down dramatically to 1/3 and 1/4 (respectively).

So if, hypothetically of-course, the examiner had to make a determination out of multiple possibilities, the "polygraph machine"'s failings would be soooo much more blatant and apparent since the examiner would be wrong the vast majority of the time. But with only two possible outcomes, the polygraph community has been able to rally support by being right even only half the time. 

The fact the polygraph has infested the government to such an extreme degree is testament to how the cocky, aggressive polygraph industry can take advantage of a government desperate and gullible enough to believe in something too good to be true (no pun intended).