It was a huge mistake to allow people to live inside DC in the first place. The National Capital that is part of no state shouldn't have anyone actually be a resident.
Each year DC pays more federal taxes per capita than every other state. In raw dollars it is more than 22 other states. [2] The people of DC want representation to go along with that taxation.
[1] https://www.publicpolicypolling.com/wp-content/uploads/2017/..., Q22 on page 6.