Sick as a dog, happy as a cat

Jon and I are taking turns wandering from room to room and falling asleep on various pieces of furniture. Musetta seems to approve. Wish I felt like a human, but just found out that "Shades of Grey" is now available for pre-ordering on Amazon, which makes it seem much more real. Why pre-order, though? Why not just available for ordering? (I'm not questioning the process – please, pre-order! Just the phrasing: Do we really need the "pre"? Can't you just "order" an item to be shipped when it is available?)