I think it would be really tough to operate without a credit card.

In my experience, the issuing bank determines at least some of the card's policies. Some are *much* more predatory and mean-spirited than others, trying to get you deep in debt and milk you dry.

I try to use my travel backup card once a year, which I assume keeps it active on their books.

I never carry a balance under any circumstances. And my cards all give me Air Miles or a percentage of my purchase back. Might as well, nobody gives discounts for cash any more.