What about having a family split over two lots? Would that not be advantageous space-wise? Also, it would lag slower computers less. Not to mention you could have two lots adjacent to each other, and use one as, let's say, a plantation. Then your sims that labour will never get the stir crazy moodlet because technically they'd leave the lot in order to do their gardening. There are many other possibilities. Nothing is useless when one thinks in a practical manner. I wouldn't be so quick to write something off as pointless.