It's illegal to use in most job hiring.

And it doesn't always work.

Polygraphs results are subjective, the only result is a human comparing some physiological reactions to test questions.

A so-called positive response only says that the person operating the test equipment believes the test subject reacted with enough similar reactions to test questions that the person being tested is likely not telling the truth.

They are not seen as reliable and cannot be used in any court.

Polygraph tests are not admissible in court and with very few exceptions are prohibited by law in employment. The tests simply are not reliable.

It has to do with the purpose of the test and reason for invading a person's privacy to such a degree. There are cases where it may be necessary, but to use it in day to day situations, such as domestic arguments or whether or not the person is lying about something on their resume is a bit far fetched. Polygraph tests are very expensive to apply and it simply doesn't make sense to use them for random day to day situations.

Edit: And sir are you telling the truth when you say at no time on the highway you drove in excess of the speed limit by any amount above 5 over,

Polygraph tests are unreliable and easy to fool.