Based on your phrasing it sounds like you think owning a national ID card is commonplace in Sweden. The national ID card system isn't widely used at all, most people use either their drivers license or passport when they need to identify themselves.
The only thing everyone has is a person number, and the difference is that it is explicitly considered public information and you can get anyone's person number by just asking the Tax Agency. It's just a convenient way to keep track of people, not a way to actually identify yourself.
The only thing everyone has is a person number, and the difference is that it is explicitly considered public information and you can get anyone's person number by just asking the Tax Agency. It's just a convenient way to keep track of people, not a way to actually identify yourself.