Why can't we just copy a successful portfolio

The portfolio of Warren Buffet owned Berkshire Hathaway has always been public. Why then we don't have millions of Warren Buffets around us? Copying a portfolio just doesn't work. Read why...BackgroundWhen I was in college, I used to study very hard. I used to sit in the college library after the classes got over, for a detailed understanding of the topics covered during the day. I often referred