That's a very generous view of the investment banking sector, and one that doesn't quite align with my 17 years experience in that line. For example, your view doesn't accommodate how GS packaged credit derivs designed to fail and sold them to AIG, then sold default insurance on the same instruments to hedge funds that would profit from their failure.
Investment banks exist to extract a profit from each transaction they do. Nothing more or less. A very large proportion of that profit goes to the management and staff of the bank as bonuses. Some of it goes to shareholders as dividends, but a much lower proportion that in other sectors. Which is why I don't buy IB equity.
You also forgot to mention how they took order from clients at one desk, then swiveled the chair around and told the prop desk what the order was so the house could front run the order or do one of any number of other unethical things to the clients.
Investment banks exist to extract a profit from each transaction they do. Nothing more or less. A very large proportion of that profit goes to the management and staff of the bank as bonuses. Some of it goes to shareholders as dividends, but a much lower proportion that in other sectors. Which is why I don't buy IB equity.