His committees of correspondence were integral to supplanting British colonial government. It was he who started the Independence movement in the first place. How come government and society today place the faces of George Washington, Thomas Jefferson, James Madison, and Abraham Lincoln on our coins and currency, but fail to include Samuel Adams? Why is Andrew Jackson, who was in favor of eradicating entire Native American populations, on the twenty dollar bill, and not Samuel Adams?
It seems Sam Adams'--arguably America's most important Founding Father--popularity has been eclipsed by the beer brand that bears his name.
Because while he may have played his part, he was far from the most important early leader. After supporting mob violence and political attacks he serves a term as Massachusetts Governor and then dies a few years after.
Everyone else you mentioned had a larger part to play. Washington of course, Jefferson was one of the 4 philosophical heavy weights (with Hamilton and John Adams, and Madison) Madison was the force behind the Constitution. Jackson was a war hero and began the process of turning the presidency and elections into truly popular affairs, and also began settling the question of state's rights. Lincoln is another which should require no explanation.
Sam Adams is arguably one of the least important personalities, he gets mad when his friends have to pay taxes and his comfy political positions are in danger, complains to anyone who will listen that people really ought to hurt those responsible, then only stays active within hi own state.