I had an OMG experience trying to look up a very interesting non-public software company on SharePost a week ago. They will offer me a chance to buy something. I don't get any clarity on the cap table, so I'd be completely in the dark on preferences, dilution, etc. I'm being asked to offer a price range before seeing any trading history. And there's no availability (at first) of any financial history.
There's potential here to make a uniquely bad investment in what might be a uniquely great company. We won't cry a lot of tears for rich people who make some bad investments in the dark. For people living closer to the edge, having them get fleeced has spillover effects that are ugly enough to argue against letting it all play out with total laissez-faire.
Especially if lax rules invite the hustlers to overwhelm the market. (Gresham's law)