Hi Gibby Jr.
Installing hard wired smoke alarms in an existing home is generally not required. However, some jurisdiction may be enforcing it if any other major electrical updates are implemented within the property, such as the main electrical service update.
You may want to call or visit your local building department and ask about this situation. They may only require interconnected type of smoke alarms to be installed which can be done without hard wiring / by using wireless, battery operated devices.