Korean entertainment trainees?

It seems that there are many people that audition for korean entertainments for JYP, SM, YG, Cube, DSP, etc. Although the audtion requirements seem not impossible, where do the people who get accepted go? I was wondering this because I'm sure alot of people audition for these entertainments but on wikipedia, (or basically the internet in general) it seems like there aren't many artists under that name. Is it because they're still training as trainees or is the auditions just that hard to get into?