the innards are often the most nutritious, we prefer the red/muscle meat, which is mostly protein and iron, because its tastier and can get the other vitamins from veg. Ever watch Discovery? Animals nearly always go for the organs first. OK partly because they go off fastest, but when there's a pack and the kill is going to be consumed that day you watch top dog going in first and straight for the organs.
Buy a turkey from a butcher and he'll give you the neck and the organs in a little bag. Makes superb gravy. Stock comes from boiling the bones, this is the base for any decent non-vegetarian soup. Lots of sauces start off this way.
here's the scottish national dish: "sheep's 'pluck' (heart, liver and lungs), minced with onion, oatmeal, suet, spices, and salt, mixed with stock, and traditionally boiled in the animal's stomach for approximately three hours." And a
good haggis is DAMN nice, anyone here who considers themselves scottish or of scottish ancestry should be having one on Friday week after next (25th Jan) - Burns night. FWIW there are some vegetarian haggis which are actually very good too, bit like meat haggis it's very hit-and-miss.
Mnay national dishes, or at least a nation's famous foods, came about from making otherwise unappetising (or even outright gross) food appealing.
Not sure i'd recommend brains though, extremely high in cholesterol.
Anyway, like Tiamat says, if you think traditional food is bad try googling the ingredients of modern convenience food.