Two things:

1. People see because they see the markets going down and want to get out before it hits bottom.

2. The bigger issue, though, is that a hell of a lot of people will lose their jobs and have no money. Remember the Great Recession? When the job market is that shitty and you lose your job, there aren’t other ones available. No job means no income. You can apply for unemployment insurance, but that only covers a fraction of the income from your last job. So people can’t afford to pay their bills. When you can’t afford utilities, rent, gas, etc, but you have a 401k sitting there, it becomes the only option to pull money out of that. It’s a super shitty decision to have to make, but when it’s a question of losing your home or sacrificing your retirement, short-term material needs win out.