There are Two Paper Towel Rolls
It's almost time to restock, but the shelf can only hold 5 rolls, so you might as well restock at an appropriate time. But you have to choose which of the two remaining rolls is going in the business end of the side-gripping dispenser.
I can choose the larger of the two rolls. The Mega-Roll. Or I can choose the standard size, which is visibly puny compared to the bigger choice. If you know the answer, it seems obvious, and that's because it's an obvious answer.
But it's not so obvious if you start thinking about why choose one in the first place. The larger roll is larger, but does that mean it should go first simply because it is preferable? The assumption is that you don't like changing rolls often and you don't think larger rolls look or work any differently than their smaller counter-part.
And maybe the smaller roll has preference, just to get it out of the way for more Megas when it's time to buy more. You need to remember to buy more. What causes you to remember to buy more? Absence or a dwindling stock. Once you get down to having one left, and it gets placed into service, you commit to memory that you need to stock up next time you remember. It's a modified version of The Game that you play with yourself, except that by remembering, you win.
The smaller roll goes in first, so that at exhaustion the larger roll has a longer opportunity for you to remember to buy more. Nothing shocks you more than an absence.