You don't need a rear windscreen wiper on a sedan. It is too far away from the rear to collect significant vacuum dirt. You'll thank yourself for not having the additional mechanical point of failure and leak point.

The rear windscreen view is acceptable with water; For snow and ice there is the defroster. However, the view through the rear window isn't essential to pilot the sedan. Think of the times you could be driving with a load that requires the trunk lid open, lots of moving stuff in the rear seats, or tall rear passengers.