Why?
Why? Do I actually have to explain why we have to protect vital industries? Do I really need to explain why we would be in serious trouble if we were unable to make our own equipment, tanks, weapons, etc? Seriously? You're being either intentionally obtuse or you really are applauding the end of the US.
have to have a means of recovering a market once it is lost.
Why? Because if you don't have anywhere to sell your goods, you go out of business. Right?
You have to have a means of retaliating against predatory trade practices.
Why? Because if trading "partners" take over your vital industries, and if they take your market, you lose. You are dependent on them for survival. Just what Marxists want. Congratulations. You have outed yourself as being either incredibly ignorant or a globo-Marxist.