why viral still use D class ?

Name Units Casualties Remaining
TheIan`s fleet
Pyth Battleship 60 60 0
D.Angel Battleship 20 20 0
V.Borrelly Destroyer 694 392 302
Pike Destroyer 160 0 160
M.Chlor Cruiser 105 0 105
Nirvana Dreadnought 8 0 8
Large Strafez Fodder 619 0 619
Tyr Dreadnought 9 0 9
Hercules 2 0 2
F.Sword Destroyer 50 50 0