I was under the impression that the 'tank top' came into fashion in the late '40s when soldiers came home from the war with them, thus the name. I do know that as recently as 1994, this was a standard issue undergarment in the USMC. As to their usefulness, we today have adopted the habit of wearing only the outer layer of clothing, where previous generations would have multiple layers. And the extra layer does not necessarily add warmth, provided that it is cotton. As many have already said, the wicking nature of the fabric actually keeps one cooler. People in the desert do not walk around naked, they wear two or three layers of lightweight natural fibers. Just last weekend I spent several comfortable afternoons wearing 3-5 layers in the lovely Independence Day sun. And a corset, which may soon come back in fashion for men... Regarding men's white shirts and opacity, many fine cottons and linens are nearly sheer. This allows circulation but also can provide a peek at one's chest hair, thus the need for an undergarment.