PR absolutely. DC never for very obvious reasons that have been well explained since the founding and haven't changed.

You'll appreciate that the current proposal on the table for DC statehood leaves a "Capital District" consisting of the National Mall and surrounding federal buildings (including the White House, Congress, and the Supreme Court), and only turns the rest of DC into a state. See the map at the bottom of https://statehood.dc.gov/page/resource-center .

If you haven't been to DC or looked closely at a map, it might surprise you that the vast majority of it is an ordinary city with residences and shops and schools, and the seat of federal government is a pretty small area. I didn't actually realize that until poking at a map and talking with friends who have lived in DC - I had the impression that DC was already small and most non-federal stuff was across the border in Virginia or Maryland, but that isn't actually true. DC is larger in area than SF!

(Also, federal districts like DC are relatively rare: most other countries don't have them. The hypothesis may not have changed since the founding, but we have a couple of centuries of experimental data now. Even the UN has buildings in Manhattan that are part of Manhattan and the US and not a separate UN exclave - I can and do bike down First Avenue, with UN buildings on both sides, without going through a border crossing.)

The reasons seem neither obvious nor static to me. The founders never intended to leave 700,000 Americans in DC without voting representation.

Are you under the mistaken impression that DC Statehood would give DC undue influence over the Federal government?