AfterBlock is self confessed as a tool thats designed to pack novelty factor, while providing games to pass the time, and offer practical services. Its about bringing Blockland out of the game and onto your desktop. Using an excel spreadsheet is not as attractive. It doesn't show a status, and isn't as easy to setup, and its not designed for such purpose. Not everyone has Excel, and the point is it offers a range of small services that are useful to Blockland in one single easy program.
I suggest that even if you still don't find AfterBlock attractive, at least reserve your final opinion until you've had a chance to try it. Because theres a lot about the program I am not releasing until its finished.