Wall Street does what they're allowed to do.
Once upon a time, we had regulations. Glass-Steagall acted as a firewall against banks owning investment brokerages and insurance companies, and was enacted after the crash of '29. Usury laws prohibited banks from making loans to those known to be poor credit risks. Monopolies were found to be not in the public's best interests, and were broken apart.
Those who felt Milton Friedman's "free market" economic policies were best began undoing such firewalls. Although primarily embraced by republicans, Friedman's policies found proponents on both sides of the aisle, with those who could benefit from associating with trans-national corporations. Phil Gramm lead the charge to undo Glass-Steagall, and Bill Clinton signed off on it (as he did with the disastrous NAFTA). The marketing push was overwhelming: they were no longer "usurious loans," now they were "an innovative set of new products."
Friedman's contention was that, if left alone and freed of restraints, the market would correct itself. The resulting uber-wealthy class would create jobs.
I leave it to you to decide for yourself if that has worked, but no less a free marketer than Alan Greenspan recently expressed amazement that the banks & wall street did not police themselves. He thought the fox would dutifully guard the hen house.
We've created lots of jobs-- in India and China. Yes, we get cheap goods from those countries, and American companies profit from having an offshore labor base. But without a job, it's hard for Americans to buy those goods.
So has supply-side economics worked? CAN it work if there's no demand because no one can afford goods because they're unemployed?
This is not a right vs left issue. It's supply side vs demand side---Friedman vs Keynes. Wall St is a symptom--the tip of the iceberg.
I'm no macroeconomist, but I will say that, to my observation, the Friedman way (a) makes no sense to begin with, and (b) certainly appears to have caused this mess.
Could we really expect society to police itself, without laws or law enforcement officials? Libertarians would probably say yes, but most of us would probably find that a not very good idea.
Yet we have expected the economy to do just that.