Nobody is forcing anyone to have a rear wiper but it damn should be an option. I've had numerous hatchbacks and every one apart from the A5 has had one and it got used a lot. I like clean windows, particularly while reversing, and I don't want to go to the shops at 90 just to clear the window. I reckon all you people that think the window doesn't get dirty 'cos you're 'going fast enough' are deluded and actually going 'slow enough' for the dirt to accumulate, or simply don't realise your rear screen is getting dirty.....Considering how fiddly the audi's are to operate I'm surprised the wiper isn't fitted and doesn't have a 3-mode toggle-switch to operate it.I've never once noticed a sufficient amount of dirt on my rear window to impact visibility. I would absolutely hate to have a rear wiper on my A5. It would look horrible.
That bugs me a lot as well. I have taken to running my finger along the bottom of the upper window trim before opening the car door. This gets most of the hanging water droplets off the trim and minimizes the number that fall into the car. Of course, this doesn't help when you are exiting the car.
There also seems to be some peculiar quirk to the design of the car that results in the trunk (boot) and rear bumper area getting extra dirty. Some sort of air flow issue seems to deposit inordinately high amounts of debris in that area.