I buy salads. Eat them with my order of super-size fries. Oh. Scratch that. My order of large fries.
Some people buy them, but the rate is pretty low. When I was there a mid-volume store averaged 2500 customers a day and sold about 50 salads a day. Salads were the least popular "main dish" and the only things that did worse overall were the cookies and grapefruit juice. Even the wildly unpopular McD and its replacement the McLean sold better. And I haven't seen any numbers coming out of McHell indicating salads are any more popular now than they were back then. The core of the burger joint customer base aren't salad eaters, and when they do want a salad they don't go to burger joints. And chasing the sald eating crowd hasn't been good for business for them.