They're probably just doing what the Royal Tournament organisers did back in the 1990s, when they decided to ditch all events which weren't relevant to the modern armed forces. (e.g. those involving the types of field guns which hadn't been used since WWI). The current activities of the armed forces don't generally lend themselves well to public displays. (e.g. using a computer to program a drone doesn't make for a great spectacle).
Those which might work well as part of a public display (such as those using helicopters) are probably either too expensive to put on or, alternatively, the relevant activities (such as helicopter search and rescue activities) are no longer carried out by the armed forces anyway because they've been privatised.