I've always been baffled at the 'last piece' cult. That piece is no more important than any other piece of the cake. What's with all the emotional baggage surrounding it?
My dad frequently eats the last cookie in the box or last piece of cake. He then leaves the container there. It's slightly different than normal "last piece" cult, but really frustrating when you're looking forward to the one piece of cake after you mow the lawn, open the container, and realize there is none left.
I agree with you -- in addition, the person to eat the "last piece" has the courage to consume the piece that is both the least fresh and has most possibly been exposed to pathogens from "other piece" eaters.
"First Piece" folks should get more flak as they've destroyed a baked work of art.
On the contrary; the first-piece person is taking all the risk of the possibility that the cake was poisoned at the factory or store. Kings had "tasters", after all.
I found this is a cultural thing, e.g. from my personal experience it is not regarded nearly as important in the Netherlands as it is in the United Kingdom.
AFAIU, when something bad happens to us, we focus our regret on the smallest/nearest action that could have been undone to change the outcome. So in this case, the bad thing being that you wanted a piece and there are none left--it's natural to blame whomever ate the last piece, because it's easier to imagine an alternate reality where the last piece wasn't eaten, than an alternate reality with some earlier piece not being eaten and everybody subsequently encountering a cake with one additional piece.
Same reason the dude who filmed the Rodney King incident was blamed for the LA Riots. People figured that if he hadn't filmed it, the riots wouldn't have happened.
It's because the person complaining likely wanted another piece, but now they can't because it's all gone. The "logical" person to blame would be the person who took the last one.
More like: "Find me the person that stole my lunch from the fridge. The bag was clearly labeled with my name! Come on people, what, are we animals here?!?!"