The main point is that food contains carbs, proteins, and fats. All foods (atleast whole foods) contain all three of these but in varying amounts. The carbs will always turn to sugar, the proteins will sometimes, and the fats won't.
When most people think of food they are thinking of something that is mostly starch (for example bread). Since starch is just a chain of glucose, and glucose is a sugar, it will turn to sugar inside the body. While protein can also turn into glucose, but the process is pretty metabolically taxing. Protein is more commonly used for other purposes. Fat will not be turned into sugar, as the body views it as a perfectly good source of energy.
A counter example you could give is that a steak is certainly food, however very little of it will turn to sugar inside the body.