Further, and this is a rather large "further," DC is prohibited from becoming a state since the Constitution states- as clear as day- that "seat of government" shall be a federal district. You can't just convert that into a state without getting rid of that pesky little clause.
You have to either amend the constitution along with the attempt to have it made into a state, or you have to declare some other place as the "seat of government." Pretty ridiculously tall orders.
The process of accepting/creating a new state is not-in and of itself- an amendment to the Constitution. It is simply the following of an existing clause in the Constitution. Eliminating the "seat of government" as a federal district would be an amendment.
No one in their right frigging mind should want DC to have two senators giving them the full weight of a real state. They may think they are special and they are. Thus the framers made them a special district.
There are other factors as well. The framers did not want the seat of government to be captive to any one state where that state could use and abuse its powers to threaten or interfere with the conduct of national matters in any way. That clearly makes sense, which means that the lefties have no chance of understanding it.