While you are technically correct in the abstract, creditors do have a method to have a debt declared nondischargeable, by way of filing an "adversarial complaint" against you in bankruptcy court. There are very strict parameters for this, most commonly used for debts incurred by fraudulent methods. As a bankruptcy attorney, I've seen a few of these pop up over the years (they are infrequently filed and even less frequently won), but they are most definitely a pain in the ass when it comes across my desk. Someone with available funds to retain an attorney for the ensuing litigation may not be frightened by the litigation (especially if they can defend the fraud accusation), but the majority of Chapter 7 debtors will shit their pants if they get sued in bankruptcy court, and may settle the case for a reduced amount just to avoid the legal fees that they would incur trying to fight the litigation.
Disclaimer: I am admitted to practice law solely in the State of New Jersey and the above is only based on my experience in that venue. I don't know how it's done in any other state.