Why should you avoid fixing your employees' mistakes?

If you fix employee mistakes yourself without addressing them with the relevant employees, you won't be able to keep track of their errors at performance review time.

If you fix your employees' mistakes yourself, you rob them of the opportunity to improve and you don't gain any leverage since chances are they will keep making the same mistake.

If you fix your employees' mistakes yourself you don't get the chance to practice having direct communication, or even confronting them over mistakes.