1) While visiting a foreign bathroom; Finding that last roll of ass wipe under the bathroom counter as you penguin walk from the toilet, panicked that you will be exposed by having to ask for a fresh roll.

2) When cash is real low, the last roll in the house, that must be rationed carefully and used for emergencies only. (No doubling up)

When you eat dirt for the first time and leave your family to build a shack in the woods