The colonists fought against the British in the Revolutionary War because they were taxpaying British citizens who were being denied any sort of representation in parliament. In other words, they were being taxed as though they were residents of Britain without being able to have any say on how those taxes were used. In winning the Revolutionary War, they won the right to decide how their tax dollars were used.
The British were treating the colonies as nothing more than a money and raw materials funnel, giving very little regard for the people who worked and lived there. All they did was take and take some more, without giving those people any say in the governance process. By declaring independence we were able to control our own destiny.