My understanding, and it may be wrong, is that until very recently Puerto Ricans were enjoying the benefits of being a territory but not a State. They were not required to pay Federal income Tax, and some of their GDP comes from having corporations there who enjoy the territorial status. Going back to the Treaty of Paris the idea of Statehood has been discussed, and generally rejected by narrow majorities. Only recently, the last dozen years or so has that changed, and only narrowly so, with a movement of abstainers from referendum always growing and skewing the vote, though that is their right and risk at the same time. I figure this is on the Puerto Ricans. If they want statehood they should clearly state as much. I do not oppose it In  any way, I just thought it was more or less an open question.
I always thought that part of the opposition to statehood is their enjoyment of their formerly independent status, and for some, even, their association with Spain, if by force. (Of course their being ceded to us was also by force) they have a unique culture and some fear losing that to gain the representation of being a State. They may figure that as a territory they already enjoy some of the benefits of statehood, or enough of the benefits, in that we provide for them a "common defense", no small matter. Still, as I say, I would provide them all of the rights of statehood if that is their wish.
As for D.C. it would be a comically small state geographically if not by population as I believe it has now passed Wyoming (Pity poor Wyoming). They have most of the benefits of statehood after the 23rd amendment was it. Also I believe it would take a Constitutional Amendment to accomplish this for them. Finally, I sort or bought the argument in Federalist 43 or maybe it was 46 as to the essential reasons the seat of government should not be beholding to any one state. Now many of those arguments were much stronger in an agrarian, pre-industrial, pre-mass communication world, but I think they sort of still apply.Â