There are a lot of people who rely on those investments, whether through their government retirement, their employer's retirement, or through their own holdings. Even many social programs are funded with investments in equities.

Slightly less than half of all Americans have any investment in the stock market. Pension funds were largely replaced with 401k's, but salaries were not increased to compensate.

While you're technically correct, the stock market primarily benefits those with enough disposable income to generate large investments where they do not need to draw down the principle, and that certainly isn't the majority of Americans.