I add a couple more spices for pumpkin pies, and I never used canned, only from a real pumpkin or squash.
I did a taste test, and people can't tell the difference if sugar/brown sugar is added, or not. So I leave that out.
I grow the little pie pumpkins and they really do not need sugar. I can well believe the stories that people used to make a syrup out of pumpkins for sweetening.