It is bad to lie about things.
Jeff is in a math contest and wrote the wrong answer to a question, then realizes that he was wrong before he answers.
Jeff wants to give an answer.
Jeff gives his actual answer and is eventually removed from the math contest.
Jeff gives the answer that everyone else gave, ignoring his actual answer on his paper and eventually winning the contest.
The best person wins the contest and gets the recognition that they deserve.
The best person, who should have won, doesn't get any prize or recognition even though they were honest.