Unfinished tombstones

When I was searching through Weston Cemetery looking for statues, I notice a number of unfinished tombstones. They were all in the older section and some of them were very large, like the Davisson tombstone that is near the bridge.
Some were mostly unfinished, like the very large Baker marker which has only a corner finished.
Others were merely large, not very large. Some had only a bit of carving left to do, like the York marker with the very attractive lily decoration.
Why, I wondered, did they do this? Was it because they bought too big a stone and then did not have enough money to finish it? OK--that is a hypothesis that only an economist would make. Other people would think that this unfinished gravestone phenomenon must symbolize something, so I went googling for the symbolism of the unfinished marker. I found a lot of explanations of cemetery symbolism (for example, here, here, and here), with some sources giving different interpretations than others, but did not find the symbolism of these unfinished monuments.
Here is a smaller unfinished marker by a Norway spruce that was toppled right after Christmas by the high winds. There is no real reason to include it except I like the dead tree behind it.
I even found one of these out in Mount Calvary Cemetery, and it was clearly carved to look unfinished, which undercuts my hypothesis that it was all about running out of money.
Maybe someone who reads this post will have an answer. If you know what this is all about, please tell us in the comments.