Why American airports don’t sell anything you actually need?

Woe betide the traveler who forgets her toiletries case, gets peckish, or has a headache at a US airport. At best, she might find tiny container of Advil or $10 packet of almonds in a Hudson News outlet, sandwiched between a Cinnabon and an Auntie Anne’s Preztels. But why is there no CVS or Walgreens