Why? The institutions that got in trouble during 2008 had no retail banking arms (Bear, Lehman, Fannie & Freddie, Merrill, etc.). Glass Steagall is a red herring. Proprietary traders were largely not using deposits to finance their bets.
The strictly investment banks (as opposed to the consolidated ones) were the ones that had the most trouble / caused the most problems in the recent recession.
This will be a response to this parent and the one that posed essentially the same point.
I don't believe I referred to anything regarding the recent recession or who was to blame. My problem with the repeal of Glass-Steagall has more to do with the overwhelming conflict of interest it could create within these institutions (i.e., using deposits to grant credit to the investment arms for making risky bets). On the flip side, you could argue that proper regulation could stymie that risk, but I'd rather just not leave it up to chance (read: politicians). That's my opinion - you may feel differently.