There is no rule, law or requirement that you must merge liabilities with your soon-to-be spouse. That means having your name added to credit cards, mortgages, or auto loans is unnecessary and has no upside. However, there is significant downside to doing so.
The minute you have your name added to any sort of credit obligation or utility, you immediately become liable for payment. You also become subject to any collection activities, should the debt become delinquent.