When America was first created we believed that there should be no taxation without representation. Essentially meaning everyone should have a voice in the government that protects and represents them.
In the case of The District of Columbia United States House of Representatives, the District is represented by a delegate, who is not allowed to vote on the House floor but can vote on procedural matters and in congressional committees. D.C. residents have no representation in the United States Senate. As a result of the Twenty-third Amendment to the United States Constitution, adopted in 1961, the District is entitled to three electoral votes in the election of the President of the United States.
If the US government intends to Govern the people of these territories they need a vote.