After four decades of deregulation and bankers gone wild, at least two of Wall Street's oldest and most prestigious brokerage houses are tentatively returning to the world of client-services-based banking. Two months ago, Goldman Sachs (NYSE: GS) announced that it will open a private bank-within-a-bank to serve its wealthy clients around the world. Now, Financial Times is reporting that fellow Wall Street stalwart Morgan Stanley (NYSE: MS) is getting a similar line of business up and running.

While Goldman CEO Lloyd Blankfein went out of his way back in July to say that nobody's going to get a free toaster for opening up a new account, the simple fact that these two Wall Street titans are moving toward more client-based services is still reason to stand up and at least offer a golf clap: It's one of the first signs that post-crash regulation is having its intended effect, and that Wall Street is returning to its roots as a service-based industry -- banking's whole reason for being in the first place.

On being a real bank, not a hypothetical one
At the height of the financial crisis, when the U.S. government was unsure if another big, interconnected investment bank was going to tumble messily into insolvency and potentially take the rest of the economy down with it, it forced the remaining pure investment banks -- Goldman Sachs and Morgan Stanley -- to accept bank-holding status. This gave them access to the Federal Reserve's discount window, theoretically stopping any runs before they could start.

It also made them, for lack of a better term, regular banks. In a stroke, they were no different from any other bank in America. This meant they could accept deposits and make loans, just like your savings and loan down the street, something they weren't set up to do before. Initially, bank-holding status was seen as a burden: It meant more regulation and the costs that came with it. Lloyd Blankfein, however, was the first Wall Street CEO to see an opportunity in the change.

"We're a bank," he told The Wall Street Journal in July. He continued:

It's not a hypothetical. [We] backed into a big opportunity. We have the regulations. We have the costs. We have the burdens. It is a no-brainer that we'll build our banking business.

And so it has. Goldman's commercial banking unit, where its private bank resides, currently has loans worth $13.8 billion on the books.

Baby steps: better than no steps
With Morgan Stanley now following in Goldman's footsteps, the barest outline of a trend may be starting to reveal itself -- one that could see a return to the kind of basic banking that still exists on Main Street, but hasn't existed on Wall Street for 30 years. You can thank bank-holding status for that, as well the Volcker Rule.

The Volcker Rule, part of the Dodd-Frank financial-reform legislation of 2010, states that banks may no longer engage in proprietary trading -- that is, trade for their own profit. They can trade only on behalf of clients, the way things used to work. Dodd-Frank is rightly criticized for being too large, complex, and unwieldy, but the Volcker Rule is fairly straightforward and is actually doing its job here -- forcing banks to find safer, more traditional revenue streams. Both Goldman Sachs and Morgan Stanley are turning lemons into lemonade, and consumers are getting a safer, less volatile banking system in the process.

This, of course, is all notwithstanding JPMorgan Chase's (NYSE: JPM) recent London Whale trading debacle, which may or may not have been in violation of the Volcker Rule. JPMorgan called the trade-gone-terribly-wrong a hedge, while others called it a proprietary bet. As such, the Volcker Rule isn't perfect, but it's the best bet the U.S. banking system has right now to find its way back home.

A big bank built to last
Bank of America (NYSE: BAC) and Citigroup (NYSE: C) almost certainly have their eye on this developing back-to-basics banking trend as well. Of course, they do the basics for their retail customers already, but why not chase the wealthy for bread-and-butter services like home loans, too? There's money to be made -- money that's a safer bet than the derivatives and collateralized debt obligations that blew up the world economy in 2008.

And safer, easier-to-understand Wall Street banks also make for better investments for the everyday investor -- the kind of investment you can get your head around and count on in the long run. But Goldman Sachs and Morgan Stanley aside, believe it or not, there's still currently a big bank out there that managed to avoid many of the pitfalls that befell its peers in the run-up to the financial crash and, as such, is one of the few big banks The Motley Fool can still in good conscience recommend as an investment.

Learn all about it in this special free report: "The Only Big Bank Built to Last." Download it while it's still available.

And if you're interested in learning more about Bank of America, be sure to check out this brand-new premium report on the company. Inside, our analyst outlines the key opportunities and threats investors have to know about and will keep readers up to speed with regular updates. Claim your copy.