The conversion of glucose to 2 mols of pyruvate and net synthesis of ATP.
An energy converting pathway that stopped at pyruvate would not proceed for long, because redox balance has not been maintained.
GAP dehydrogenase uses NAD+ and there are limited amounts of NAD+ in the cell.
Therefore, NAD+ must ne regenerated for glycolysis to procees.
Thus, the final pathway in glycolysis is to generate NAD+ through pyruvate metabolism.