Because it leaves the industry vulnerable in case China decides to start withholding sales to the US. Especially if they invade Taiwan and trigger a chain reaction of treaties that launches into a huge US vs China slugging match. One which China would likely lose painfully to, but would inflict crippling damage to our military. Anything coming out of China will be stopped for as long as the war goes on, and then even longer depending on how much of what I'm China actually got destroyed.