It's more that what happens to the Dow day-to-day or even week-to-week is not really relevant to most people, even the ones with 401(k)s since it's about what happens in the long term when you're worried about retirement.
So a single day major point drop? It's really not a big deal to anyone but the investor class.
Now if this is the start of a long-term trend, that's another issue. But we can't possibly know that yet.
If it happens again, the government will bail out several companies and in some more serious cases they will end up under state guardianship. However, politics will be turbulent in that scenario.