On a Roll

Why is it so hard for someone to change the toilet paper roll? People seem to have a strategy when it comes to doing that. Normally someone uses a few squares to clean themselves. Let's use 10 as a base number. When the roll starts to dwindle, it is decreased to 7. As the roll gets almost to the cardboard, it goes down to the amount that looks like there is still paper on it, but there is not enough for one use. This forces the next user to put in a new roll. Yesterday, in both work and at home, I was the one to change the roll. It is not a big deal, but it just irks me that that task was left for me when it was clearly the job of the previous person.