You need to pay more attention. There are many a stock Zeev has made a pretty penny on that was suggested by somebody else. With 8000 or so stocks, how many can one person keep track of. How many relevant news articles can one find and read. And what better way to keep striving to be better than to display the results for all to see. Think discipline. It's very much a two way street.
If you're doing a forecast just for yourself, might you get sloppy and lazy. If hundreds or 10's of hundreds are going to be reading it, you're probably going to triple check your numbers. I don't know why people keep questioning why Zeev does what he does. He has more than once enunciated on it. How blunt does he have to be? Just because some are better than others doesn't mean there are ulterior motives.
One could ponder, is it possible to get better in a vacuum? But better itself insinuates a comparison. Better than what? Is it not the challenge that spurs one on to higher heights? And the challenge of just oneself can get old.