You're making a big assumption that "putting them all on the same side" has ever been seriously considered or that, were it considered, the result of jamming up

You're making a big assumption that "putting them all on the same side" has ever been seriously considered or that, were it considered, the result of jamming up gas stations was considered. Without empirical evidence to support these assumptions, Occam's Razor would have me believe that it's as simple as: nobody's really thought about it (other than, as pointed out above, to balance the suspension in high-performance vehicles).