I recently realized that nearly all problems in codeforces have multiple test cases in a single test, which makes my code ugly and annoying.

I wonder why codeforces set multiple cases in a single test?

I know some OJs will do this because they don't have better machine to run many divided cases. But it is obvious that codeforces' judger runs well.

In some contest rules they set multiple cases in order that participants can't get unexpected points through tricks, like presenting only "Yes" or "No", or print a random number. But codeforces' rule doesn't work like this.

So is it a tradition to do so or for other reason?