I get it. I carry "0" balances, so I would have a lag time of up to 30 days before I had to pay anything and if I paid it then, no interest. I do not believe that I have ever paid interest on a credit card.
Beyond that- yeah, they are going to get hit with interest. Again, not pleasant, but this is the way life works sometimes.
I keep zero balances too. But I buy just about everything I can on a certain card that gives me back enough bonus cash to pay for my ammo needs. Then I pay it off every month so I don't have to pay interest. That way I can tell my wife, no honey, I didn't spend any money on ammo this month.