You’re at a friend’s house and use the toilet. You notice the toilet roll has been placed on the holder so that the paper rolls under, not over. You remove the toilet roll and place it back on the holder so that the paper rolls over. Aaah, now that's better. Sound like you? That’s okay, because according to Seth Wheeler, the individual credited with ‘inventing useful improvements in toilet paper rolls’ back in 1891, the ‘over’ position is the correct way to hang your toilet roll.
Seth has even kindly provided a useful diagram to illustrate the correct method of hanging your toilet roll.
Other reasons for hanging toilet paper in the ‘over’ position includes reducing waste (as it’s easier to see the tearing point) and hygiene. Although the latter is not scientifically proven, some don’t like the idea of toilet paper touching the wall of the toilet, due to germs that could be present on the wall from flushing the toilet without putting the lid down.
You’ll also notice printed toilet paper is designed to be placed in the ‘over’ position. You’ve spent a little more on the print, so it makes sense to hang it in the right orientation so that you can admire it.