Like a ski resort full of girls looking for husbands and husbands looking for girls, the situation is not as symmetric as it might seem. Many states are "right-to-work" states where an employer may fire freely, just as an employee may quit freely. ("Right-to-work" being quite the misnomer.) However, quitting is when one employee abandons every other one in the company, and being fired is when every other employee in the company exiles one. Firing or a lockout is much more drastic than quitting or striking, and needs an entirely different legal status; that's why we have laws preventing employers from discriminating on the basis of race, gender, or religion.
It's also instructive to note who wound up in what situations after Hurwitz bought Kaiser with junk bond financing, and then sold and closed factories and cut wages and benefits to pay off the debt. The old owners were richer. Hurwitz was richer. The old workers were fired. And the new workers had lower pay and benefits. And that is why the Kaiser Aluminum story is considered to be bad business, and why unions, the folks who gave us the weekend, are not to be dismissed lightly.