Also, I would point out that middle classes typically (and by definition, according to some definitions) make money from skilled labour, not investment. Stock profits is just not that big a percentage of a middle class person's lifetime earning.
It should be noted that half the US has no 401K. 80% of stock is owned by 10% of the population. So "middle class" really means "above the median" if we're talking about people with any substantial stock investments.
Also, I would point out that middle classes typically (and by definition, according to some definitions) make money from skilled labour, not investment. Stock profits is just not that big a percentage of a middle class person's lifetime earning.