From American Banker magazine from a while back and out of paradigm but still relevant.
"One of the many problems with a high leverage ratio stems from the flight to safety during periods of stress, which causes bank deposits to soar. Since 2008, while the U.S. economy has struggled, deposits have risen by $2.6 trillion, often with pronounced temporary spikes that remain on a bank's balance sheet for just a few weeks. A recent example of this occurred during the politically charged debt-ceiling crisis. At that time, deposits jumped by $73 billion, according to Federal Deposit Insurance Corp. data. Deposits provide crucial funding for all banks, but as deposits surge, bank leverage ratios drop. Worse, sudden changes in deposit flow make banks' leverage ratios volatile. Most banks simply manage this volatility by staying well above the current leverage ratio requirements. That is, they are generally over-capitalized."