The only reason for multiple banks, imho, is either for features or for insurance.
Banks only provide $100,000 FDIC insurance per account title. If you're married you could have an account, your husband an account, and you could have a joint account together. Three accounts all titled differently and you have up to 300,000 in FDIC insurance in one location. Some provide brokerage accounts which are covered with additional insurance agencies (SFIP I think) and again, altering the titles provides additional insurance.
Some prefer some features to others. The whole free checking, free billpay... umm, should be a given. But what about hidden fees if I want to X, Y, or Z? If you maintain a minimum balance you shouldn't have to pay a single cent. A free toaster, radio, etc are all just scams to get you in the door, imho. How much are checks with duplicates when I need them? Do you call me if there's suspicious activity on my account? Do you call if I write a large check "just to be sure". Those are true features. Keep the radio.
My husband loves US Bank, and I hate them. With US Bank I get charged the stupidest little fees continuously and if I complain I'm told I didn't "sign up" for a feature. Elite at US Bank means ****, imo. Now, I love Bank of America - I get great service with Advantage. They know me and greet me by name at my branch (that I rarely go to) and I never pay for anything they even match a percentage of check card rollover transaction in savings. I'm biased...
At least if everything is within one bank, you can easily transfer between accounts. Cashier checks to different banks is time consuming (and some charge to receive wires?!)... though BOA (again, bias) doesn't even charge to send them!