Why some cars have gas tank fillers on the left or the right

Jalopnik:

Quick—which side of your car is your fuel filler on? No running outside to look, that’s cheating, and you might get hurt pulling your pants on. Chances are most of you at the very least had to take a moment to think about this. I suspect you won’t think long about what side your steering wheel is on. That’s because, unlike other crucial parts your car, there is no standardized place for what side you pump fuel into your car. Why not?

This is one of those things you don’t think about but, when it gets explained, makes a lot of sense.