The primary reason the British government taxed the colonists was to raise revenue to pay off the significant war debt incurred during the French and Indian War (1754-1763). The war had been costly for Britain, and the British government believed that the colonists, who benefitted from the protection provided by the British military during the conflict, should contribute to the costs of that protection. This led to several taxes and acts, such as the Stamp Act and the Townshend Acts, which were met with outrage and resistance from the colonists, ultimately contributing to rising tensions and the movement towards independence.
While it's true that many colonists felt that the British government was taking advantage of them, the direct rationale behind the taxation was largely focused on addressing the war debt and the costs of maintaining British troops in North America.