As most things, they are both a scam and a tool. It is like a gun, if it is pointing your way is probably something you would not like.

Cards are a tool when you use them to buy stuff you need to work or go to work or somehow produce a return or if you make sure you pay everything at the end of the month. If you do anything else, particularly buying stuff you do not really need (really really need) and then pay the minimum... you are going to learn first hand what is the "rat race".