Spreadsheets let you click any field and understand where it came from. Excel can be thought of as an amazing post-execution debugger where you can get a previous output and value for almost any piece of memory ("cell"). I would love a debugger that could do this post-execution for some output.
In this case even getting 99.99% of the way there is still practically worthless, as someone will be interacting with Excel millions of times throughout a career.
