Or more likely, the Spitfires are 70+ year old 'geriatrics'. Why risk overstressing an airframe just to show how fast and furious you can fly?
I remember reading in Douglas Bader's biography, Reach for the Sky, that he forbade his pilots doing victory loops after witnessing a pilot die after having the tail section of his Spitfire come off whilst doing one after returning from a combat sortie. Mind you, I could be mistaken about the source as I read the book some 50 years ago.