Deorbit fuel is a relatively tiny amount, and you don't gain much from refueling in orbit for that. The Shuttle deorbits using just its orbital maneuvering engines, and I think (not sure) there's even an emergency procedure to deorbit using just positioning thrusters.

Refueling in orbit is how you get to the far places, or GEO orbit.

If launches are cheap enough to LEO, launching fuel from Earth becomes practical. Refueling satellites, which use dense exotic storables, is the probably the most cost-effective near-term application. You can gas up a lot of satellites with not much fuel. The problem there is that satellites have to be refuelable, and you lose a lot of economics because you have to haul the fuel into GEO.

Launching liquid hydrogen into orbit is a pain because it requires huge tanks for little propellant mass. One school of thought is to launch water into orbit and crack it into fuel on orbit using solar power. At some point in the future it might become practical to crack the fuel from ice on the Moon and launch it to refueling points using catapults.