Utah law holds both spouses responsible for "family expenses", including the cost of medical care, so the hospital presumably wants to see if you have the resources to pay them before agreeing to write off the debt.
Quote Quoting Utah Code, Sec. 30-2-9. Family expenses - Joint and several liability.
The expenses of the family and the education of the children are chargeable upon the property of both husband and wife or of either of them, and in relation thereto they may be sued jointly or separately.