Do people really do that? I mean use their credit card as an actual bank loan, paying off their credit cards in installments, with interests?

I've been using credit cards for the past 15 years, and never paid a single cent of interests. In fact, in my Central European country it is quite common to own a credit card simply for added convenience and safety, but I do not know anyone who does not pay their debt on time. In fact banks here even offer you the "autopay" option, so at the end of the month the balance gets paid off automatically, so you can avoid any charges easily.

For context apple offers 0% apr financing on many of their products with the Apple Card. If one has the means to buy a new iPhone with cash, why not take the free ~40 bucks you can get by using Apple Card financing and keeping the cash in some other extremely low risk place (eg an FDIC insured high interest savings account like the one Apple Card offers)

I'm doing it right now. I quit my job to bootstrap my SaaS last year, and it's been messy. There was a lot of churn after a competitor released a major feature free that I was charging for.

Some months, my income has been pretty low. I've withdrawn from my 401(k) and gotten a loan through Stripe Capital. Still, there've been times when there are so many fires to put out that I end up without enough money in the accounts to pay off the card at the end of the month. So, after 10+ years of never paying interest, here I am.

I'm sure there are better ways to do all this, but I didn't know them and I don't have connections, though I'm working on all of that. That's just how it's played out over the past 12 months.

most people intend to pay off their card every month. but people who run into financial problems or just have a tight month financially will often pay less on their card. and there are a lot of those people.