The companies that are too immature to do SOX just simply don't deserve to IPO.
It has very little to do with maturity. Just like the Patriot Act, SOX was an overreaction. It adds layers & layers of red tape & costs (even if it has "worked", which I don't know one way or the other). While it has certainly weeded out some bad companies, it's discouraged some good companies from going public as well.
Interesting to see that 2004-2007 there were over 150 IPOs. 2008 has just 20, roughly half venture backed.
And the 2000s still look sickly, at about half the trend of 1980-2000.
M&A has taken a blow too (article is slightly dated):