There are many arguments but the most straightforward one is that a country may decide that preserving particular industries is in their security interest. That can be extended to culture as well.

Japan closed itself off from the world for centuries during the Edo period. One could say that they suffered economically due to that, but on the other hand, they ended up creating one of the more unique cultures in the world, developing in ways very different from others. It's an interesting kind of diversity.