> If there's a famine or a meat shortage, wouldn't people turn to other foods on their own?

Encouraging weekly fish-eating habits is also a mechanism to ensure that you have a healthy national fish industry, that you can dial up as soon as you need it.

This is something that modern [especially European] nations seem to have institutionally neglected or forgotten.

By importing all necessities and instead focusing on exporting services, you put your nation and people at risk from any such crisis.