They are part of the Nobility Perks Suite of contractual features for all nobility to enjoy. Features include: Functional immortality excepting the subclass of hero and/or a preexisting ban and/or a death duel. Absolute lack of requirements for food and/or waste removal (This can be observed when in a starving region. Your soldiers will starve. The peasants will starve. You will never need to worry about food because there will somehow always be food for you). Immense stamina allowing you to do things continuously for at most 16 hours with only 8 hours in between for sleep and other stuff.
Yeah, this is mostly for game convenience. After all, who would like it if you had to dedicate a few hours actively to things like acquiring and eating food, going to the toilet, and sleeping (Granted, for the last one, depending on the pace at which you want to play, you might have to do that actively as an adventurer).
So the whole dropping your unit in a city so that they don't fight over gear sounds like a package deal. That reminds me of the time I once had a unit that was 100% equipment damaged, yet never got injured from that. It was interesting.