In 2012 this was relaxed in JOBS Act which relaxed the 500 threshold to 2000 but more importantly it ignored employees so now private companies of gargantuan trillion dollar valuation and thousands of employees have no disclosure requirements.
So, this is a classic case of regulation that did well but was relaxed and now creates hidden risks.
[1]: https://www.investopedia.com/terms/5/500-shareholder-thresho...
We have historical data on how it worked out for companies that were pushed into going public by the old regulations... Microsoft, Google, Facebook, et al.
Their early stage employees did... pretty well... financially.
The only real difference from the employee perspective is that a lot of the money that made them rich came from public investors (who also had a chance to make a lot of money), whereas now it only comes from private investors and the public is locked out.
I'd say it's the growth of private markets to allow companies to keep getting funding even at the $100 billion range while staying private that has fueled the trend to stay private rather than SOX and other new regulations for public corporate governance dissuading them from going public.
Which regulations are these?
It's not that you couldn't stay private before, but there wasn't much benefit because after crossing that cap you had reporting obligations comparable to public companies anyways.
>Regulations that limit the ability of investors to invest in private companies ...
The JOBS act raised the cap from 500 investors to 2000, but with VC funds, that's hardly an issue. Does Anthropic (and other unicorns) really need 500+ VC backers? It might change behavior on the margins, but it's hard to imagine that's the cause for the paucity of public listings.
The actual change that made it more tenable to stay private is arguably the carveout for employee stockholders, but summarizing that as "limit the ability of investors to invest in private companies" is a bit misleading.
Before that change companies like MS were in essence forced to IPO, because they'd get all the downsizes of public reporting, without the benefit of accessing market liquidity. So once you were over the threshold, it made no sense to not go all the way.
That's no longer true, and has coincided with a huge expansion in private equity funding growth stage companies vs needing public liquidity. As a result these IPOs being done after their growth stage is largely over are offering the public a very different bet that tech company IPOs of the past.
My guess would be - oxytocin, cortisol and dopamine regulation, or rather the failure of said regulation.
This also coincides with a growing market for private credit and VC which certainly helps companies stay private for longer.