Anyone know why the fuel selectors on single engine low wing airplanes never have a "BOTH" selection. It's always left or right which begs for human error. Just curious because high wing gravity fed planes have BOTH... why can't low wings have the selector bring both fuel tank lines into a manifold that is pulled by a machanical fuel pump / elec boost pump? Even new low wing singles have not come out with a both fuel selector. What is it about the low wing that restricts this capability. It can't be just that they are not gravity fed like high wing.... there must be some other design factor that limits this ability. Anyone who thinks they know please chime in...Thanks in advance for all constructive answers.