Why can’t someone make a heat exchanger pot or pan where the combustion air is vented away like we do with gas water heaters and furnaces? It also never sat rig

Why can’t someone make a heat exchanger pot or pan where the combustion air is vented away like we do with gas water heaters and furnaces? It also never sat right with me that there’s a giant tank of near-boiling water in our garage, yet we use a ton more energy to heat up cold water for cooking.