Why are they books destined to disappear?

Little reflection on the disappearance of hundreds of directories of links in the Google index. This loss often resulting in a simple downgrade in the SERP. Why launch directory? Why Google does it hunt these FarmLinks?
First of all why is it interesting for a webmaster to create a directory?
In a web where content is king, having a site where content is created by users themselves is extremely tempting.He is drooling young webmasters on most forums, is that referencing frantically add the site to directories to gain the maximum possible connections and thus make progress in the serp search engine.The clientele of the directory is there, just create a few posts on the forums to see its directory receive content.
Why Google is hunting for directories and attempts to make them disappear from the index?
Small matter of logic. Google wants an engine light, fast, relevant steps ... you your research, you find what you seek!It is not in their interest to send users to another list of links, another search result.
A small example of the disappearance, one of the largest web directories that the majority of French webmasters know is not even present in its domain name.Big-annuaire.com (I hope the webmaster will not mind too much to quote?) Was present on dozens of very large requests (some of which I am aiming for that reason I noticed this decommissioning) and generated heavy traffic. Its traffic is still important because of its many backlink but one year was divided by 4 according to alexaThe problem is not to have a directory, but to base a network of directory sites only because they end up falling ;-)
So much for my little personal reflection ... agree, disagree express yourself!
Other section of the web portal on directories that do not share my conclusion: Directories