First, Banks aren't an investment platforms. Though some banks are being listed on stock exchanges, the bank itself isn't an investment platform, but they act as a storage of your money so that they can protect your money. That's the problem right now. Many people really thought that it would be better to put your money in the banks, and just let it stay there for the sake of safety, but little did they know that the value of their money is slowly going down because of inflation. They don't know this because of lack of financial literacy, and the banks are taking advantage of it.
Second, helped millions of people? Well, maybe some people got some help with the banks, but that's their to cover up what they really are doing. They are profiting on your own money thru lending it 10x (fractional reserve banking). Just imagine this. You're being fooled by the banks, you store your money there knowing that they can keep it safe, and on the other hand, they are lending out your money to other borrowers, and getting profit from it, while you the depositor loses money thru inflation. What a shame these banks are doing to most of the people out there.
Well, I guess old people are the ones who taught that putting your money in the banks is the way to go. For us new generation, putting it in the banks is a no-no (or at least for me). Even though I have this hate feeling for banks, I'm still using them right now as a storage of my emergency funds (kind of ironic).