sick kid and grocery stores

How come whenever I go to the grocery store to get a huge cart full of groceries they have a bunch of express lanes (15 items of less) open and very few regular lanes open? And now today, when making an emergency trip to buy crackers, jello, and Popsicles for a puking kid, they only had regular lanes (really backed up with people with huge cart fulls of groceries) open and no express lanes?

Sometimes the universe laughs at me...