Source: some Matt Levine article.
I don't think it's helpful to anyone's understanding of any situation to try to pretend that tens or hundreds of millions of Americans -- who are on the whole somewhat wealthier than average -- are mega-rich snobs who drink ten-thousand-dollar-a-bottle wine.
1) Indirectly via mutual funds, pension funds, and so on.
2) Directly through buying individual stocks on E*Trade or the like.
The second amounts to an expensive hobby (in risk adjusted terms). Whether some people who aren't ultra-rich choose to indulge in such an expensive hobby is neither here nor there, the underlying fact remains that there's no good reason to care about or optimize for their benefit. Yet for some reason so many articles on this subject instead of talking about the funds that are broadly and rationally held, analyze the situation for the small retail investor.
http://www.csmonitor.com/Business/2013/0508/Dow-hits-15000-b...
The rate of stock ownership (including through mutual funds and retirement accounts) for Americans is around 52%, down from last year. So, while the median American owns some stock, it's probably a minuscule amount. Two percentage points lower, and the median American (Joe Six Pack) owns no stock.
EDIT for more related info:
45% of Americans have no retirement savings [1]
1/4 of Americans have no savings whatsoever [2]
[1] http://www.twincities.com/ci_23505006/americans-retirement-s...
[2] http://www.ibtimes.com/over-fourth-americans-have-no-money-t...