laundry soap and milk??

What is deal with laundry soap and milk? Sometimes a gallon of milk will sit in our fridge for a week and no one will touch it, but the minute it is gone - all of sudden we can't cook, we can't make cereal, everything needs milk. Same with laundry soap. I go a few days without doing laundry and the minute we are out everyone needs something washed or we are out of towels. Its crazy to me how this works.