How "expensive" is a baryon particle sweep? TNG's "Starship Mine" suggested that prolonged velocities at higher warp speeds build up harmful radiation residue that somehow needed to be neutralized.
It's inconclusive at what time in-universe this problem was acknowledged and how they dealt with it in the 23rd Century. I believe they did not have baryon sweep technology in the 23rd Century and simply sent the hulls for cremation into the nearest star or sun (too bad the ex-Soviet Navy couldn't do that with their nuclear submarines).
Contamination might be an issue to consider.