There concrete reasons to use one in Europe (at least where I live):
It's a month's free loan - why spend your own money when you can keep it invested or otherwise working for you for a month first for free?
Consumer credit law is still stronger for paying on credit than on debit.
I used to fly transatlantic first class once a year for free based on just my credit card rewards. I'm not some unusually high earner either. What possible reason is there to turn that down?