The main reason why the Articles of Confederation did not give authority to collect taxes to the Congress was because the colonies did not want to lose their autonomy and independence. The United States was not established as a federal country, and it took some time before the colonies could agree to cooperate more fully.
Eventually, it was recognized that limiting the ability to collect taxes would mean that the Congress would not be able to effectively fulfill its duties. Moreover, this could leave the colonies vulnerable to attacks. The issue eventually led to the Constitutional Convention and the Constitution of the United States.