Sometimes the wind doesn't blow. Unfortunately, this often happens on those hot hazy sweltering days when the demand for electricity is at its highest. So, you have to have enough supply without wind-energy to cover those times, so what good does wind do?
Maybe the tech types can come up with cheap Terawatt-hour energy storage, so power generated on windy days could be saved for a sweltering day. Pumping water uphill into a reservoir for hydro power later might do it, but the economics....