"A customer should be able to walk into a financial institution and get any financial product he or she needs — securities, insurance, banking or trust services,"
A Broker would know what was in the securities they sold and would not like to have his or her reputation tarnished by selling crap that backfired in a couple of years.
Allowing the banks to pick, train and direct the "brokers" allowed them to pick any smuck and train them the way they wanted them trained and teach them only enough to sell the crap without telling them enough to know that what they were selling was crap.
The banks made money off the sub primes they wrote. They rolled them into securities and sold them to buyers.
The Broker rules were put in place under glass steagal, so they could not do that.
Press Release: SEC Votes for Final Rules Defining How Banks Can Be Securities Brokers; 2007-190; Sept. 19, 2007