I was just going to vote on the poll and leave it at that...
But if you really want a reason, it's because the game wouldn't fit cubecraft well. It is a big complex game with lots to keep track of and small details that need to be perfected. This would like take forever to code (based on decent evidence) and I don't think it would be a success. Most games on cube are fairly simple to learn and complex strategies are made by the players. They aren't required to play the game. A game like sister-locations requires lots of skill in forms of reaction time, memorization, and specific movements. The people who have played through sister locations have spent hours upon hours beating some of those levels. I think if this was added to cubecraft, it would end up like blockband, with only a few hardcore players actually playing the game. Along with the fact that it would be a Halloween game and those tend to get removed a few weeks after the event.
To me, it just looks like a lot of work for not that much reward.
Happy now? :p