The historical windmill design gave flexibility because the windmill can be turned to catch the most wind depending on the direction it is blowing. The blades were constructed by hand and placed at just the right angle to catch the most wind.
Windmills have changed little over the last hundred years. In fact, one basic design conceived in the 1870s is still sold today. The major improvements have come in the types of materials used in construction. This trend will likely continue in future windmill products.