One version of Excel across all platforms
Why do we have 'Excel for Android', 'Excel for Mac', 'Excel for ...', etc.? The user experience of Excel should be the same across all platforms.
Kenneth Barber commented
Not to mention that it will probably make programming and maintaining Excel a lot easier. Most other cross-platform programs don't have radically different versions with large discrepancies in features.
Let's not forget the discrepancies between the 32-bit and 64-bit versions as well: