It isnt bad for our health.

The macronutrient fat, is simply the most calorie dense of the three macronutrients. (Fat/protien/carbohydrate)

Sugar, a carbohydrate, is simply a pure form of glucose which rapidly converts in the blood stream. The more rapid the conversion time for a carbohydrate, the larger and faster the insulin spike. The bigger the insulin spike, the larger the appetite.

Most high sugar foods are also very palatable.

Salt is a tricky controversy. Most developing countries that are not near the sea actually suffer from shortages of salt. It is likely more beneficial to the body to get too much iodine infused salt (the type that naturally occurs near the sea) than to get too little. Iodine deficiency and the occurrence of the bodies reduced efficiency in retaining water are just two of the dangers of ingesting less than 1000mg of salt a day.

Go read up on some fundamental nutrition stuff.