Sure you could, but while you're busy trying to find the exact combination of spacing and punctuation that starts the loop you want, and then manually looking through the loop to find every further reference to the same variable, the guy who called it "ii" and found it with the first four keystrokes is already being productive.

As I said before, it's probably not as useful with modern IDEs that have semantic search capabilities, but there is a genuine reason some people prefer the "ii" style.