The issue is that AM radio is far more reliable in an emergency:

in a true emergency, seven former FEMA administrators wrote in a letter to Secretary of Transportation Pete Buttigieg, the signals that power AM radio are more reliable than FM, phone service, and internet connection. Most of the 75-odd stations with backup communications equipment and generators that allow them to broadcast in a crisis are AM stations, and AM radio covers 100 miles or more, far more territory than FM or any other widely accessible alternative. Source