It is about balance, independence and longevity of the nation. A diverse economy is more able to resist economic challenges of ALL types. It is also able to res

It is about balance, independence and longevity of the nation. A diverse economy is more able to resist economic challenges of ALL types. It is also able to resist sudden turns in foreign policy (war) and maintains options for such a country if they find themselves at war with the country that supplies their manufactured goods or their services, or whatever it may be. Additionally making things, providing services, whatever it may be, develops with practice, into the arts. If we don't ever have that practice we lose the ability, as a nation, to develop those arts.