Because it's not an even split. Sure, I could buy that, on average, energy use grows in proportion to economic growth, but some activities (e.g. services) I'd

Because it's not an even split. Sure, I could buy that, on average, energy use grows in proportion to economic growth, but some activities (e.g. services) I'd expect to have much less energy use that others (e.g. manufacturing). And, when you look at actual data, e.g. https://www.eia.gov/todayinenergy/detail.php?id=33812 https://www.eia.gov/todayinenergy/detail.php?id=33812, that is exactly what you see.