I know, I just posted an update, but it doesn´t happen every day that I´m getting offended on behalf of an entire planet in outer space.
Arrakis is a desert planet without water and the population (not the ruling house, of course) has to suffer because of this lack of water. So the former ruling family, the Harkonnens, thought this custom to be a good idea:
Flanking the doorway in which he stood were broad laving basins of ornate yellow and green tile. Each basin had its rack of towels. It was the custom, the housekeeper had explained, for guests as they entered to dip their hands ceremoniusly into a basin, slop several cups of water onto the floor, dry their hands on a towel and fling the towel into the growing puddle at the door. After the dinner, beggars gathered outside to get the water squeezings from the towels.
Apparently Duke Leto Atreides is just as offended as I am and how I admire his character for this:
"I know the customs!" he barked. "Take these basins to the front door. While we´re eating and until we´ve finished, each beggar who calls may have a full cup of water. Understood?"