Why?

Given that the English drive cars fueled by petrol, whether leaded or othewise, or LPG or deisel (and very, very occasionally in Highgate and Hamstead and Notting Hill and Chelsea Village a hybrid) why oh why do commentators, when wading into the 'environment/go green/cars and planes are going to be the death of the planet' debate, insist on referring to low mileage vehicles as Gas Guzzlers?

Why?

They're usually the same people who blame the world's environment ills (and most of the others too) on the US.