Well not the least because you need these alternative sources when the wind doesn't blow or at night. For all the noise about including externalities in the cos

Well not the least because you need these alternative sources when the wind doesn't blow or at night. For all the noise about including externalities in the cost of oil, the quoted cost of solar and wind almost never includes the infrastructure you would have to build and maintain to deal with the intermittent nature of the source. Worse than that, grid scale storage capacity isn't even being built in the countries deploying wind at scale. It looks like a strategy for a country like the UK if the intention is to keep relying on carbon (LNG) in the long term. But if the intention is to switch off carbon, there is a massive cost in the pipeline to deal with intermittency.