Open holes in areas of sheetrock walls or ceilings that connect the home to the garage must be sealed for fire safety reasons.  The sheetrock walls and ceilings separating the home and garage are considered a fire separation barrier, that must be maintained for safety reasons in the instance of a fire.  The fire separation barrier, in case of a fire, would slow down the fire’s progress throughout the home and allow for less damage (before firemen can put it out).