For stuff like "this line doesn't make sense next to this other line. Why was it added?" Sometimes a line was deleted between them, sometimes it was a bad merge, sometimes the rest of the commit tells you "oh, it was added to make the Foobar work."

I have allocated some of the valuable left-hand-only keyboard shortcuts in my IDE to searching Git history. It tells you the "why" when the "what" doesn't make sense, and the "who" when git blame shows some reformatter.