The biggest reason would be that the people of Maryland oppose retrocession. [1] You cannot make Maryland take back land they do not want without something like an amendment to the constitution.
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.
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.
[2] https://statehood.dc.gov/page/why-statehood-dc