They are only worth it for certain types of card holders. It wouldn’t make much sense for you to have a card of the kind unless you spend a lot of money. These cards usually come with higher interest rates as well and annual fees as well and as such they usually cause the holders to spend more than they should and that’s what may cause certain holders to get in debt.

So unless you earn enough of the points to actually offset the additional cost which is generally rather hard, you will always end up with a negative balance, rendering the cards a bit useless.