Regarding a banks capital requirements you can to the FED's website and read them. A bank's capital is required to be a certain fraction of assets (their is type 1 and type 2 capital so there is a minor complication here). Assets means debt owed to the bank. I can create a bank, and acquire a deposit by selling paper in the money markets, acquiring say $100,000 (purchased by a someone who paid me money from a checking account to purchase). I effectively acquire a $100,000 deposit from this, and there is no reserve requirement for me to lend this. I can then lend this out at interest. But my bank capital in order to make the loan must be about 10% of the loan I am about to make. This is not a monetary think, but a separate regulatory thing.
This little think about capital is why you and I cannot just go into the banking business tomorrow.
Oh, and you and I can go into the banking business tomorrow, easy as pie, and reap all the rewards it offers to the largest established economy of scale and world class franchise, top tier credit and huge customer base, etc. Just buy Citi, Bank of America, or JP Morgan shares, Monday morning.
Since it is easy to partner with the existing banks, anyone who prefers to lend to them (hold bank money deposits) instead of share their risks and their rewards, has no just cause for complaint about them. If they have a deal so good it is a scandal, join them. If, on the other hand, a ride so rocky in sometimes means 50% drops in less than a year puts you off enough that you prefer CDs, don't complain that they make more money over the long haul, than the CDs do.