Do you have a source of the pre-SOX company IPOs vs post-SOX company IPOs? I'm more curious than anything. SOX didn't just eliminate fluff it eliminated many profitable companies who don't have the earnings and market size to justify going public. This is fine by me - going public is overrated anyway.
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.