In a nutshell, because the USA is a capitalist society that's governed by rule of law. So regulators don't get broad power to approve or deny any business deal

In a nutshell, because the USA is a capitalist society that's governed by rule of law. So regulators don't get broad power to approve or deny any business deal based on ad-hoc decisions about whether they think the deal will ultimately be a net positive for the economy 10 years down the line. They get much narrower powers to protect against a specific set of things as laid out in whatever laws comprise their job description. And Congress doesn't usually get involved until after there's already a big smoking crater surrounded by a bunch of upset people. And don't think that the supply of "smart, creative people in a position to capitalize" is limited to the CEOs of unicorns or anything like that. The supply is actually the total number of entrepreneurial-minded people with an idea and a desire for some capital to help get it off the ground. And the scope of ideas is not limited to silicon valley startups. I'm talking about people the pool of money could throw its funds at, not the (much smaller) set of people it has thrown its funds at in the past, or the (even smaller) set of those people who get bashed in the news.