Most of the gas isn't used for generating electricity. Rather, it's used at the point where the electricity would be used. If you build a house you can install a furnace that gets joules from the electricity network or from the gas network, see? And there are a little over ten million houses and apartments that get their warm water and heating from gas-heated boilers/furnaces.

See https://www.haustec.de/heizung/waermeerzeugung/waermemarkt-w... for example. There's also the chemical industry, which uses gas as chemicals, not as a source of joules.