Transporting gas is always tricky. Even in a contained unit as the gas trucks they come in (liquid in general is hard to transport), it can be dangerous. Not as in exploding, but that is always a possibility, but as in how do you get it from point A to point B? Or where do you store it, trunk, seat, do I hold it? What happens when you go around a turn?
Gas sloshes around, and when you go through a turn, it moves with the inertia of the car and can spill at that point.