Over the holidays I made several major purchases using my bank card rather than cash or a credit card. I'm sometimes surprised that more people don't use their bank cards (or "cash cards" or "ATM cards" or however you want to refer to them) as debit cards, since most can be utilized that way. Of course the retailer has to accept debit card payments, but I've found that many larger ones do.
The advantage of using a debit card is obvious. There's no need to carry large amounts of cash, and charges are immediately subtracted from your bank account, or on the next business day if you're making the purchase on a weekend or holiday, or at night. Actually, some people may find this latter point a disadvantage if they aren't always sure how much money they have in their account at any given moment, in which case a credit card might be better since the withdrawal (assuming you are using your card as a deferred payment card and not as an actual credit card) won't be made until the next month or whenever payments are normally made from your card-specific account. But I think most people have a good idea how much money is in their account. The most important consideration is that it doesn't cost you anything to use a debit card.
Which may explain why banks don't really promote them. These days banks aren't really making money the old-fashioned way, meaning through loans. More and more rely on services, and one of the primary services is ATM fees, which are often difficult to avoid. If you're withdrawing cash and the ATM you're using is not operated by the bank with which you have your account and/or it isn't done during standard business hours (usually 9-6) then the chances are you're paying a fee to access your money. And if you're doing some other kind of transaction, like sending money to another account, then you're even more likely paying a fee, and a fairly steep one.