> And how do politicians use the stock market to take money from anyone?
Insider knowledge.
> How do rich people make money in the stock market if it's a "scam?"
They have an army of traders and their job is to buy and sell non stop, taking advantage of smaller players who think the game is fair, until a profit appears.
> What about index funds, which usually have proven returns and require no special knowledge?
Why don't everyone buy into index funds then (genuine question) ?
They should, unless they have an “edge” over others, such as inside information or analysis that others did not do or did incorrectly, such as checking satellite photos of parking lots (in days prior to delivery).
If you do not have an edge, then you are simply gambling. But I would say craps is more fun. Low cost index funds like VOO are just true inflation protected securities over 5+ year timeframe, in my opinion, because you know the US federal government is going to pull out all the stops to prevent its biggest organizations from collapsing.
There's actually been a bunch of articles over the last year or two talking about how the large number of passive investors in index funds is causing an issue for price discovery of individual stocks.
And everyone doesn't do it because some people are ok with taking more risk for more return.
I'm still not sure in what form this "taking advantage" happens. I think the stock market provides unique opportunities in how one can start small and grow with additional capital, knowledge or time when it becomes available.
> Why don't everyone buy into index funds then (genuine question) ?
For a variety of reasons: some find it boring, some think they can beat the index, some get stock grants and stick to what's familiar, some buy stocks that they hear about (because their friends do), etc. Even those who (mostly) buy into index funds may invest a chunk of their portfolio into riskier assets.