Why are fats useful and sometimes better than carbohydrates

As compared to carbohydrate and proteins fats has more than twice a calories per gram. A gram of fats has 9 calories. A gram of carbohydrate and proteins has about 4 calorie. Therefore, fats useful and sometimes better than carbohydrates.

Fats contain more than twice chemical energy as proteins and carbohydrates have. So sometimes fats are very important than carbohydrates or some other biomolecules.