The simple answer to your question is this: regulation.
The U.S. Securities and Exchange Commission (SEC) prevents hedge funds, private equity firms and other private investment managers from marketing their products to a wide audience.
High risk funds, like the Medallion Fund, are limited to fund raising to an exclusive group of investors that must meet the following criteria:
a) those with a net worth of at least $1 million excluding their primary residence, or
b) annual income of more than $200,000 in each of the two most recent years.
The deeper answer to why the SEC does this is: protection of the 'lowest common denominator' investing public.
By and large the investing public are not what you might call:
1) 'professional' (keeping an eye on the market as part of their job), or
2) 'sophisticated' (as in have a knowledge of the multitude of securities, how they work and how to trade them), or
3) Have a high risk profile and matching capacity for loss.
I think these points, from the SEC's point of view, make the selling of the Medallion fund to the general public inappropriate. I would imagine that from the SEC's perspective, the Medallion fund would be a 10/10 risk profile (highly speculative) and therefore the SEC would want an investor to make an investment fully understanding what they were investing in, and having enough wealth to suffer a total loss of money invested.
This leads into another point, the wording of your post implies that the 'astounding' annual average of 38% net of fees is practically a 'sure thing' when you say that since the fund's launch it took one drawdown in 1989.
However, you miss the obligatory warning that past performance is no guarantee of future results.
Speaking as a retail trader I can quite happily say that for different levels of risk I can make (and have made) the following returns (net of fees):
a) 1% per month with a high level of confidence with what I would call a very low risk trading strategy (annualised to 12% per annum),
b) 2% per month with a medium to high level of confidence with what I would call a medium risk trading strategy (annualised to 24% per annum),
c) 3% per month with a low to medium level of confidence with what I would call a medium to high risk trading strategy (annualised to 36% per annum), and
d) 4%+ per month with a low level of confidence with what I would call a high risk trading strategy.
The point I'm making here is that:
* If you know what you are doing,
* You have the capital (and capacity for loss), and
* You have the risk profile,
Then you can make decent market returns too. Technology has democratised the markets so there really isn't any reason for being negative and bothering about inequality.
You would however have to work for it and if the Medallion Fund are making 82% per annum (38% + 44%) before management fees they are working extremely hard for that.