Why do alanine and lactic acid enter the cellular furnace at the pyruvic acid stage?

Alanine and lactic acid can be converted into pyruvate in the cell through various metabolic pathways. Pyruvate is a central molecule in cellular metabolism and can be further metabolized through the citric acid cycle to produce energy in the form of ATP. By entering the pyruvic acid stage, alanine and lactic acid can be utilized by the cell to generate energy.