That's because a working electricity system fueled mostly by wind turbines requires additional massive costs that a fossil fuel system does not: huge excess capacity (
perhaps 300 - 400 %) to deal with conditions of light wind; gigantic batteries to store power for conditions of no wind at all, which can persist for days; extra transmission lines to bring electricity from windier areas to the rest of the country; and finally, an entire array of fossil fuel back - up
plants for those occasions when the wind doesn't blow for a week and the batteries are
dead.