adaptability

if all military aircraft were vtol capable, then there would be a lot of options were to place a temporary military airbases in areas where there is asphalt and sufficient infrastructure for equipment and personel 

if aircraft could be modified to use gasoline as aviation fuel, that could be a benefit or if gasoline could be converted to aviation fuel with small scale equipment

either way, when aircraft become electric, fuel will not be an issue, just pull electricity from infrastructure in area or use space based solar 

even if an air force has air dominance and ability to use air bases in more secure areas, it's wise to be able to have those options that vtol capability offers