Now that I think about it, there's a strong selection bias here. Private companies are, well, private, and don't get very much news coverage. Many super-profitable private software companies that never took investment are undercovered by the media. 90% of the successful software companies that I meet at conferences like Business of Software have never come within three states of a venture capitalist.
Rather than looking at how many rich people took investments, it's more meaningful, in deciding whether or not to take VC, to look at the outcomes of founders who take VC.
Those outcomes are not disputed... about half fail outright, the rest mostly continue as zombies, a tiny number make the founders a million or two, and a very very very tiny number become big enough hits to make the founders truly wealthy.
I think you have to look at this comparatively though. The number of rich people is by definition small.
To make a comparison worth anything at all is a problem. While you might or might not like thinking of VCs as a filter, they do perform this function to an extent.
If your non-VC sample consists of mostly VC rejects, that's a problem.
Rather than looking at how many rich people took investments, it's more meaningful, in deciding whether or not to take VC, to look at the outcomes of founders who take VC.
Those outcomes are not disputed... about half fail outright, the rest mostly continue as zombies, a tiny number make the founders a million or two, and a very very very tiny number become big enough hits to make the founders truly wealthy.