The referendums they held were boycotted by a huge majority of the population and due to the low turn out not considered valid. There is a VERY strong anti-statehood movement in Puerto Rico and a minority that want full independence and a minority that want statehood.

The Puerto Rican government chose not to pursue statehood based on the low turn out, but the option is still available to them anytime. This has nothing to do with the USA federal government and everything to do with Puerto Rican politics.

Too many politicians in Puerto Rico benefit from the corruption and low taxes to allow statehood.