The jury system is intended as a brake upon the excesses of government. It is a part of keeping 'we the people' the fourth branch of government.
"I consider trial by jury as the only anchor yet imagined by man, by which a government can be held to the principles of its constitution." --Thomas Jefferson
"The jury has a right to judge both the law as well as the fact in controversy." --Chief Justice John Jay, 1st Chief Justice, US supreme Court (Georgia vs. Brailsford, 1794:4)
"It would be an absurdity for jurors to be required to accept the judge's view of the law, against their own opinion, judgement, and conscience." --John Adams
"It is not only [the juror's] right, but his duty, in that case, to find the verdict according to his own best understanding, judgement, and conscience, though in direct opposition to the direction of the court." --John Adams
Why do you think they want us to forget this...
You better check Marbury vs. Madison.
The critical importance of Marbury is the assumption of several powers by the Supreme Court. One was the authority to declare acts of Congress, and by implication acts of the president, unconstitutional if they exceeded the powers granted by the Constitution. But even more important, the Court became the arbiter of the Constitution, the final authority on what the document meant. As such, the Supreme Court became in fact as well as in theory an equal partner in government, and it has played that role ever since.
Juries don't get to decide the constitutionality of laws.