Markets can recover. If you invest in stock you have to consider that you may not be able to liquidate it within the next 10 years. What if the markets don't recover? If they don't recover you will have far larger problems than your stock portfolio being in the red. The machines and people don't just disappear unless there is a war.

Even if you fail to do that as long as you have started investing sufficiently early enough - let's say 30 years before retirement (around 35 years old) - you probably have experienced at least one recession and recovery until retirement. If suddenly markets crash during retirement by 50% on an asset that is up by 150% does it matter? You still got away with a profit.

And nobody forces you to liquidate everything at once. So sure if you plan to draw out 4% of your stocks you will have decreased your portfolio by 8% every year.