When I graduated college, I furnished my apartment with furniture paid for with 0% financing on the Stør¹ credit card. Reading the fine print, if I didn't pay off the card in full by the end of six months, I would be charged some outrageous interest rate (over 20% IIRC—but this was 31 years ago so I could be wrong), backdated over the life of the loan. A lot of 0% financing works on similar bait-and-switch terms. If you look at the fine print on auto financing deals, it often requires a high down payment and short loan term and it's there more to get people into the dealership than anything else. Those few who are able to actually use it are considered an advertising cost.

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1. Stør was similar to IKEA but Danish and a bit more downmarkt

By the do you mean you’re paying the “interest” cost of the loan as part of the sticker price? If so, that’s not always the case.

I used to offer 0% and absorb the cost of the financing (which cost me approx 2% of the profit) because it meant purchases from people who otherwise wouldn’t buy it.

Not always! I buy everything, including food shopping, on 0% credit cards and keep the money in savings accounts earning interest. I always have a matching amount in savings as the balance on credit.