Why are gas tanks on different sides of the car?

Why are the gas tanks on different sides of the car?
What is the point of that?

:S

This is one of those things I wish they'd standardize. It used to drive me crazy when I drive an unfamiliar car to the gas station and have to guess which side it is on. A few years ago auto makers did throw us a bone by putting an arrow to the left or right on the fuel gauge to indicate where the cap is. Seems to me it is most logical to put the gas cap on the left side of the car so drivers can drive on the right side of the pumps (since we are used to driving on the right side of the road (sorry UK drivers)).

When I was a lad many cars had the gas cap hidden. Some were hidden under the rear swing-out license plate and some were even under a tail-light lens. There were even old VW Beetles that you had to open the trunk to put gas in them.

That still doesn't answer my question

It is all in the design of the car. Different engineers have different ideas on what they want to have and where in any design they come up with.