It's not only wasting energy that the wind turbines could be generating. Power grids also have to maintain reserve and contingency so that if the wind suddenly dies everywhere (unlikely, but possible) they can more or less immediately compensate so the grid doesn't desynchronize. This is very expensive and inefficient. A storage solution that is co-located with the turbines would be optimal, as the best sources of wind are often far from urban areas. This means that quite often even if the power is required by the grid, it can't be used as grid constraints don't allow it. Violating grid transmission constraints leads to drooping power lines and cows exploding in fields (this is not an exaggeration).

Source: I designed the control room systems for electricity balancing for National Grid in the UK.