This is a good question.
I think it is ignorance on the part of those who somehow chose what to commemorate. Civil War is forgotten.
But more importantly, the black vote as a bulk whole is more important.
Raising awareness of a war in which so many Americans died to free blacks might open the eyes and minds of a few too many black voters.
The leftists need the near unanimous vote and even a small percentage change throws elections back in the R column.
Freeing the blacks was a consequence of the war, but it wasn’t its purpose. The Union Army soldiers would have deserted en masse if they thought that the reason they were taken from their homes to suffer all of the vicissitudes of war was to free slaves.
You may know that The Emancipation Proclamation applied to
only southern blacks. Northern slaves were still not free!