I always thought it is obvious - it was done so that it will be well visible on predictable background patterns. Otherwise (if it would be a clean vertical, hor

I always thought it is obvious - it was done so that it will be well visible on predictable background patterns. Otherwise (if it would be a clean vertical, horizontal, 45 degree design) it would easily "hide" in plain sight, sticking to grids, window borders. Blend in too easily.