Answer:
Because these people did not necessarily see taxes as a wrong thing in itself.
Step-by-step explanation:
What the American revolutionary leaders did not agree with was paying taxes to the British, because of the lack of American representation in the British parliament (no taxation without representation was their slogan).
When the United States was born, and styled as a republic, and a democratic republic, these American leaders did not see anything wrong with people paying taxes to the new American government. This was not a tyrannical, undemocratic foreign government, but the very government that guaranteed American citizens many civil and political rights.
It was only to be expected that American citizens should contribute to the functioning of the new nation.