Why do people do this to firearms, specifically those with historical value!? situations like this just make me mad.
Well, you don't know the condition of the original stock, either.
It might have gotten broken in half, run over by a wagon wheel, stomped on by a horse, or who knows. But you can bet it was something serious or it would have been repaired in some manner. So the restock, as poor as it might seem, at least kept all the original parts together, even if the re-stocker wasn't a great gunsmith.
Without the restock, a trash heap would have likely been the resting place for all the parts.
John