Because it is for the SEOs to find out. SEOs would be useless if Google leaked the algorithm used for indexing the sites.
Actually... it was leaked many times... and lot's of people spammed the google serps because of that ;0
Essentially what google does is only to "tweak" already. The basic algorithms can be found in any book on information retrieval.
Yes KingSEO... but we are people, people have brains, so we can easy make tests, analize the results... and try to break down the algortims
google has published a lot of information, but a lot of it's simply red herrings. it's more complicated that simple information retrieval as well. that doesn't explain exactly how trust works, exactly how the sandbox works, exactly how they value which links as being more relevant, etc. SEO's have to reverse engineer. it works, sure, but we only use it because it's the best option we have available. what I'm saying is, from a statistical standpoint, I find it hard to believe nothing's been leaked, be it from human error, lack of security, or some combination of the above.
if google algorithm to be released, are there smart people who can understand this algorithm? but no fun. this is like coca cola secret. i think, which have designated certain people are paid well and keep this code only for google.