1) This is due to the fact that proteins in the human cell are synthesized from amino acids, which are formed during the breakdown of food proteins during digestion. Essential amino acids required for protein biosynthesis cannot be synthesized from fats and carbohydrates.
2) Carbohydrates and fats can be synthesized from proteins supplied with food, therefore, their deficiency is not observed.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.