> If I use a credit card, I pay up to 20% on the outstanding amount.

Key is never having outstanding debt. Pay your credit card balance in full. Most people with credit cards do this. I have never met anyone who paid any interest on their credit card because everyone I know pays it in full each month.

> And I have never met anyone who had a fraudulent charge (without being dumb).

And? The point is if it happens, you are far safer with a credit card than a debit card. Once the money is gone from the credit card, it's the credit card companies problem. Once the money is gone from your debit, it's your problem.

> To me, I cannot understand why anyone would use a credit card unless debit isn't accepted.

Because credit card is more secure. As the OP already told you.

As long as you have financial discipline, using a credit card is smarter than using a debit. It's a simple concept.

Paying your credit card off fully every month ensures you don’t pay any interest (use it like a debit card). Wrt the earning interest point, consider that with a credit card you still get interest on the money you don’t spend, and you can also collect interest on the money you do spend (eg I buy something for $100 on the 15th, I can collect interest on the $100 until I have to actually pay the bill on the 1st of next month). Not to mention that you also pay 1-1.5% less for everything you use a card for due to cashback schemes. I definitely see why it might seem weird the way Americans use credit cards but it is mostly rational.

Yup. For a responsible user there simply is no downside to using a credit card in most situations.