In theory, Wall Street should accrue value in two forms: as a tax for the liquidity they provide, and as compensation for the risk they take. It used to be that the investment banks were mainly middle-men, but increasingly they've also become essentially government-backed hedge funds. Unfortunately, they can use their position as middlemen to extra value from Main Street. Finance should not be like 10% of your GDP, unless you're Switzerland or another country that "exports" banking services. It doesn't produce value itself, it's just a tax on the rest of your economy necessary to ensure the availability of capital.