Hi Mark
We will agree to disagree on this one

. Bear in their are many unhistorical aspects to the game and this might only be one of them if you wanted to address this one then we should address others. Also its arguable.
I like using the low quality units to attack as well as the guard as high morale is really better for defense.
Many armies on the defensive or back foot used their guards liberally.
Napoleon in 1813, 14 and 15 used the guard extensively in every way really
Before that the Russian guard saw action at places like Austerlitz, Borodino and others
The Austrians really did not have a guard but used their powerful Grenadier btns liberally
The Prussian guard fought in 1806 as did their grenadier btns
The various confederation of the Rhine guard units fought extensively in Russia in 1812
The British guard fought at Waterloo
As always using the unhistorical argument is in my view open to endless debate. Anyhow no worries mate!