I figure that any food you get in a 'fast food' restaurant is going to be less healthy than food you cook at home. Your priorities at home are to use what you have in the fridge to create dinner. But a fast-food establishment has to deal with a whole different set of requirements. If you let a buch of buns go stale, then you either eat 'em stale or throw them out. Costs you a couple of bucks. If McDonalds lost a day's worth of buns, that's a lot of bread. Similarly, you may buy higher-quality groceries; people mentioned chuck vs. round. A few cents a pound isn't a big deal if you're buying a couple of pounds, but have you considered how much meat these places prepare in a day? Cents on the dollar matter at those scales. I'll pay a little more for better ingredients, but I'm not buying hundreds of pounds of hamburger meat either.
And people don't often look at nutrition info when they want fast food. I like Checkers' fries. They're deepfried, battered potatoes, loaded with salt and fat. Are they health food? No. I also don't eat them more than about once a month -- because they're not healthy. But people pick fast food for taste, convenience and speed. Popular stuff is loaded with sugar, salt and fat -- because sugar, salt and fat taste good. Fast food places sweeten their food because it makes the food seem to have more flavor. Ditto on the salt and fat. But if you go to a four-star restaurant, guess what? They do the same thing, only with butter and cream instead of partially hydrogenated soybean oil. Same game -- boost the fat, boost the flavor. Fast food places do try to engineer their products to cater to what people want -- y'know, to sell product and make money. But so does the fancy chef's restaurant -- people buy food out to get something tasty. That's what they want, and restaurants want to provide that.
You want health food, you have to eat at home, or pack a lunch. Or find one of the earthy-crunchy stores that sells sandwiches. (Note though, that avocado sandwiches are not low-fat

But if you want a hot meal, that you can get into your hands in a minute or two, then fast food is out there. Wendy's has a baked potato which is good until you slater it with sour cream and margerine. Salads are great until you douse 'em in salty, fatty ranch dressing.
(edited to fix my Quayle-spelling of potato)