Actually, there's a pretty interesting economic divide [here in the States] between white and wheat bread, due to a number of historic factors.

Currently whole-wheat or brown bread tends to be consumed more by people of middle-or upper-class background; by contrast, bread prepared with processed wheat (white bread), which is less expensive, is more often the choice of working-class consumers. The reason for this difference is a historical reversal of fortune. The white flour was once that of the elites, who would even color it with alum. The highly refined flour was reserved for those with great status, whereas the whole-grain flours were those of the poor. Source

As these things often do, the white bread trickled down from the higher classes to the lower classes. Then we found out white bread is unhealthy, leading to a proliferation of older-style breads among the upper classes, while white bread maintains its popularity and "American-ness."

Also, the 1950s ruined all food, especially bread.