You're absolutely correct. Think of it like this - if you're paying a lot of money to get the top people, you'll want to use their brains. Simply put, retail banking does not provide comparable returns on investment than putting the people into hedge funds, trading, etc.
You have to bear in mind that banks (from my personal experience and from my peers) are first and foremost profit oriented, which effectively guides their decisions. Hence, you'll not see those people working on things that directly impact retail customers.