Why don't Puerto Ricans pay United States Federal Income taxes?

Puerto Rico is an island in the Caribbean that is occupied by the United States, even though much of its culture is a representation of Spanish culture. Although it is an occupied territory of the United States, it is an unincorporated state, meaning that it is separate from state authority. That is why Puerto Rico is not considered a state, even though many politicians have been trying to make it the 51st state of America. Since the island is not one of the states of our country, it is given no representation when it comes to public office and elections. The people of the island are not granted a vote, and most don't even seem to care. And since they are garnered no representation, then they are legally able to no be subjected to income taxes by the government. This is a prime example for use of the famous quote: "No taxation without representation!" But don't worry, the Puerto Ricans still have to pays import duties and taxes, and I believe they still have a mandated sales tax and property tax, so it isn't like living there would be totally tax free.