Why do wind power plants have just 3 blades?

Question

Why do wind power plants have just 3 blades? It seems that adding more blades would increase the area that interacts with the wind and gather more energy.

_{(Image from Wikipedia.)}

Answer 1

It is just easier, i.e. less expensive, to build and maintain them that way. There exist alternative designs that are more efficient but also more difficult (= more expensive) to build, put up and maintain. You can check those out via this link.