[loa_in_]

Binary diffs are not useful, unless the diff software understands the underlying format. Most formats are linear but many are not, and many formats permit different binary encodings of equivalent data. Imagine for example archives created from same directory tree but by different implementations. There's no reason to develop this feature in git, because that's a lot of maintenance for little to no use. I don't see why spreadsheets should be any different. If they contain plain text that should be diffable you can remove non printable characters and pipe it to diff.