This is pretty much the practice in telecom. The reason is that metals corrode when more positive than surrounding electrolytes and plate when more negative. Positive ground simply reduces corrosion of exposed wire and connectors. Metal gas pipelines often have high current power supplies to maintain a negative charge on the pipeline relative to ground so they last longer. In automotive environments, the tadeoff is corroding the wiring or the chassis. My guess is that positive ground was abandoned because the metallic chassis connections end up being harder to maintain than the insulated wire connections so it was more favorable to make the chassis more negative.