Puerto Rico has rejected becoming a state 3 times since becoming a commonwealth of the United States and rejected our naval and army bases. They do not relate to America and are their own culture.
Keeping Puerto Rico as a territory is only continuing a financial burden on the states. To create statehood will cost the US a great deal in taxes. The average Puerto Rican family income is less than half that of our poorest state's citizens, statehood would require an extensive federal funding; over two-thirds of Puerto Rico's population lives below the federal poverty level.
Those coming from Puerto Rico go through the same immigration process as others from the Caribbean.
Puerto Rico has a better chance at development on it's own, where it can embrace it's own culture & history