- With a debit card, I am out $X of my own money, until the bank can be bothered to agree that the charge is fraudulent and refund my money, which can take weeks or months, if at all. Good luck paying rent or buying food or whatnot in the meantime if you don't have a nice savings cushion.
- With a credit card, I am out $0 of my own money, and now the bank is potentially out $X of THEIR own money, making them significantly more motivated to investigate promptly and agree that the charge is fraudulent. For however long this takes, I still have my own money to pay rent and buy food, and I'm not on the hook for paying the fraudulent charge.
The fact that credit cards tend to have "rewards" in the form of cash back or airline miles or whatever is secondary to me, personally, although I do take advantage of this as much as possible.