I’ve heard many of the peeves people have about Costco. They will not have a "fast lane" (10 items or less) probably ever. It’s not part of the business model. They want you to make a field trip out of it and stock up. That inexpensive bottle of wine, those developed photos, the birthday cake, the fresh flowers, the newly released book, video or CD… that’s get you in the door and you will wait with one item or a hundred. As far as low fat items, they are not as popular so they are not sold. Costco limits its "SKU’s" (inventory units) to about 2000 (compared to Walmarts 100,000+) to get the best price, display it the best, turn it the fastest, control inventory, freshness, and keep it stocked up. They also rotate items based on the upcoming season as well as drop items that don’t meet sales expectations. It’s all "real estate" in those warehouses and every item "pay rent" based on their margin. Suppliers even pay for the end caps (the aisle side displays).
Costco has a forumla that works and keeps members coming back. The shoppers that go three or more times a month will find the "gems" that are items they acquire in a one time deal and sell at great prices.