Yes, Culebra and Vieques islands are both part of Puerto Rico. So they are not part of the USVI and that is why clearing customs is necessary when arriving from the USVI but not Puerto Rico in these two islands.

The problem seems to be lack of basic necessities like food and water, as is the case with Puerto Rico and the other hurricane affected islands.

Tourism provides an alternative and sometimes necessary income but the local people need to be able to live before tourists strain the infrastructure beyond the current capacity.