1) Over a kitchen window (because you damp mop often, you might not want long drapes).
2) Over a Jacuzzi tub area in a bathroom.
Other than those areas, full length drapes are often the best route for a window treatment, because if they're hung in the right place, and in the right style, drapes make the window look taller and wider, and in return, this makes the ceiling look taller. They don't require a valance above the drapes, as these photos will indicate. Sometimes less is more!
Full length drapes instead of a valances.
with valances instead of drapes. The valances did not
look appropriate in a nice master bedroom, as they
made the windows look to small.
This window treatment felt too skimpy
in comparison to nice full draperies.