Why do the cells in your body never use nucleic acids as an energy source?

Getting energy out of organic molecules requires a specific mechanism.  That mechanism is cellular respiration, and because of its specific enzymes, their locations, and characteristics, it works most readily on carbohydrates.  If the amount of carbs runs low, then fats will feed into the same reaction pathways, and ultimately, amino acids from proteins, as well.  But the body would undoubtedly be dead by the time all those resources were consumed to the point when nucleic acids would be broken down.  But theoretically, it could happen.

Bc nucleic acid is used to make proteins and without proteins you wouldn't survive. If you used your nucleic acid for energy, then you wouldn't be able to produce proteins