Cars etc are earthed during refuelling.
The fuel pump is bonded to earth.
The fuel line is conductive.
The pump nozzle is electrically bonded to the fuel line.
The car's fuel tank and filler neck and bonded to the car chassis. The car's tyres are loaded with carbon to make them electrically conductive - if they weren't massive static voltages would build up on the car's body during a journey.
Probably not a perfect earthing system but I don't think you could rely on the car owning public to attach an earthing strap to their car every time they refuelled.
Don