Because cold winter days exist. Yes you can only build nuclear capacities for the average day and then short-term storage to match the demand pattern. But you would need to do so for the day(s) of the year with the highest energy demand, some cold winter work day. What do you do with those capacities the remaining year as throttling nuclear down is not really saving much costs (most lie in construction and deconstruction)?
Because cold winter days exist. Yes you can only build nuclear capacities for the average day and then short-term storage to match the demand pattern. But you would need to do so for the day(s) of the year with the highest energy demand, some cold winter work day. What do you do with those capacities the remaining year as throttling nuclear down is not really saving much costs (most lie in construction and deconstruction)?