The Vatician is a city State, so why can DC be a state of the USA. Though if the people of DC want to be their own state why shouldn't they be one. Sure some might argue that it could start similar ovements for cities in other states pr regions of other states to try and become new states but the key difference is that DC residents do not have representives who have voting rights in Congress.
So perhaps the "smart people" should be saying why in 2016, DC residents don't deserve representives with voting rights. I suspect it has little to do with constitutional matters as the US constittuion can be ammended and more to do with it might favour one political party over the other.
Don't get all lathered up, sheesh.
Other cities could not petition for statehood because they are part of existing states.
The district was designed to be a separate entity from the rest of the country. DC has a representative, just
not a vote on the House floor. That rep is able to participate, and presumably vote, in committees, and lobby the entire House on behalf of DC. The district is represented by the whole of Congress. Adding a voting seat to the House wouldn't make much difference either way. But adding two seats to the Senate might, maybe. But DC already has three electoral votes, so the outcome is negligible.
The cost of seating a governor and legislature would likely necessitate a huge increase in taxes, since the thirteen seat council headed by a mayor would probably no longer be sufficient to govern a new state. Taking the federal government out of the equation would probably mean the creation of new bureaucracies which would also need to be funded. The impact would be hardest on the least able to handle such an increase, as always happens with new and higher taxation. With a population of only about 900K, the demands would soon exceed the ability of the citizenry to pay.
There
would be new jobs for professional politicians and bureaucrats, though. A government paycheck and the pension they always seem to build into it would attract those who had worn out their welcome in Congress and public-funded agencies. Most of those types already live in DC anyway, so it's no big adjustment.
I could go on and on, but I'm sure no one really wants to hear about the down side.
I'll end with this opinion and be on my way: If DC were to ever become a state, the citizens would get much more than they bargained for, and not in a good way.