Duck
After the Helderberg disaster, the regulations governing "Combi" aircraft were significantly changed. While out of my area of expertise, those who are in the know have told me it would be close to impossible to certify a new Combi style aircraft to the updated regulations.
All the Combi's currently in operation where certified prior to the regulations being updated in response to the Helderberg.
As DR notes, military operations do not need to comply with commercial certification restrictions.