You’ve just finished shopping and now you’re returning the shopping cart. You’re then faced with the situation as shown in the picture below. In which lane do you put the cart?
I always choose the one with the lesser amount of carts in it (in this case the left one). Perhaps you think there is no difference where you put it. But I like to believe that there is. If you put it in the lane with most carts in it already, this causes the difference to become bigger. And if this goes on for a while, at some point that difference will then become very noticable and attract even more carts until some employee has to make an extra effort to move a number of carts to another lane (which is inevitably a hassle). So the end result is that the cumulated amount of time and effort spent on something stupid as shopping carts is higher. And I want to avoid that, if only to allow someone somewhere to spend those 15 minutes in a better way.
(Sorry that by now you can no longer return a shopping cart worry-free.)